Along those lines, we are adding provisions to 40 CFR 86.1821-01 to
clarify how manufacturers need to separately certify vehicles above
14,000 pounds GVWR by dividing them into different families even if
they have the same design characteristics as smaller vehicles. This is
consistent with the way we have been certifying vehicles to evaporative
and refueling standards.
    Second, we are modifying the test procedures for vehicles with fuel
tank capacity above 50 gallons. These vehicles have very large
quantities of vapor generation and correspondingly large evaporative
and refueling canisters. The evaporative test procedures call for
manufacturers to design their vehicles to purge a canister over about
11 miles of driving (a single FTP duty cycle) before the diurnal test,
which requires the vehicle to control the vapors generated over two
simulated hot summer days of parking. We share manufacturers' concern
that the operating characteristics of these engines and vehicles do not
support achieving that level of emission control. We are therefore
revising the two-day diurnal test procedure at 40 CFR 86.137-94(b)(24)
and the Bleed Emission Test Procedure at 40 CFR 86.1813-17(a)(2)(iii)
to include a second FTP duty cycle with an additional 11 miles of
driving before starting the diurnal measurement procedure.
    Third, manufacturers pointed out that the existing test procedures
don't adequately describe how to perform a refueling emission
measurement with vehicles that have two fuel tanks with separate filler
necks. We are amending the final rule to include a provision to direct
manufacturers to use good engineering judgment for testing vehicles in
a dual-tank configuration. It should be straightforward to do the
testing with successive refills for the two tanks and combining the
measured values into a single result. Rather than specifying detailed
adjustments to the procedure, allowing manufacturers the discretion to
perform that testing and computation consistent with good engineering
judgment will be enough to ensure a proper outcome.
    Table III-23 summarizes the cost estimations for the different
technological approaches to controlling refueling emissions that EPA
evaluated. See Chapter <IP_ADDRESS> of the RIA for the

details. In calculating the overall cost, we used $25 (2019 dollars),
the average of both approaches, to represent the cost for manufacturers
to adopt the additional canister capacity and hardware to meet our new
refueling emission standards for incomplete vehicles above 14,000 lb
GVWR. See also Section V of this preamble for a summary of our overall
program cost and Chapter 7 of the RIA for more details on our overall
program cost.

          Table III-23--Summary of Projected Per-Vehicle Costs To Meet the Refueling Emission Standards
----------------------------------------------------------------------------------------------------------------
                                                            Liquid seal                   Mechanical seal
                                                 ---------------------------------------------------------------
                                                                   Dual existing                   Dual existing
                                                   New canister    canisters in    New canister    canisters in
                                                                      series                          series
----------------------------------------------------------------------------------------------------------------
Additional Canister Costs.......................             $20             $15              $8              $8
----------------------------------------------------------------------------------------------------------------
Additional Tooling \a\..........................               0.50
                                                               0.50
----------------------------------------------------------------------------------------------------------------
Flow Control Valves.............................               6.50
                                                               6.50
----------------------------------------------------------------------------------------------------------------
Seal............................................               0               0                10
----------------------------------------------------------------------------------------------------------------
    Total.......................................              27              22                25
----------------------------------------------------------------------------------------------------------------
a Assumes the retooling costs are spread over a five-year period.

    Incomplete vehicles above 14,000 lb GVWR with dual fuel tanks may
require some unique accommodations to adopt onboard refueling vapor
recovery (ORVR) systems. A chassis configuration with dual fuel tanks
would need separate canisters and separate filler pipes and seals for
each fuel tank. Depending on the design, a dual fuel tank chassis
configuration may require a separate purge valve for each fuel tank. We
assume manufacturers will install one additional purge valve for dual
fuel tank applications that also incorporate independent canisters for
the second fuel tank/canister configuration, and that manufacturers
adopting a mechanical seal in their filler pipe will install an anti-
spitback valve for each filler pipe. See Chapter <IP_ADDRESS> of the RIA for
a summary of the design considerations for these fuel tank
configurations. We did not include an estimate of the impact of dual
fuel tank vehicles in our cost analysis of the new refueling emission
standards, as the population of these vehicles is very low and we
expect minimal increase in the total average costs.

IV. Compliance Provisions and Flexibilities

    EPA certification is a fundamental requirement of the Clean Air Act
for manufacturers of heavy-duty highway engines. EPA has employed
significant discretion over the past several decades in designing and
updating many aspects of our heavy-duty engine and vehicle
certification and compliance programs. In the following sections, we
discuss several revised provisions that we believe will increase the
effectiveness of our regulations.
    As noted in Section I, we are migrating our criteria pollutant
regulations for model years 2027 and later heavy-duty highway engines
from their current location in 40 CFR part 86, subpart A, to 40 CFR
part 1036.\314\ Consistent with this migration, the compliance
provisions discussed in this section refer to the final regulations in
their new location in part 1036. In general, this migration is not
intended to change the compliance program specified in part 86, except
as specifically finalized in this rulemaking. See Section III.A.1.
---------------------------------------------------------------------------

    \314\ As noted in the following sections, we are finalizing some
updates to 40 CFR parts 1037, 1065, and 1068 to apply to other
sectors in addition to heavy-duty highway engines.
---------------------------------------------------------------------------

A. Regulatory Useful Life

    Useful life represents the period over which emission standards
apply for certified engines, and, practically, any difference between
the regulatory useful life and the generally longer operational life of
in-use engines represents miles and years of operation without an
assurance that emission standards will continue to be met. In addition
to promulgating new emission standards and promulgating new and
updating existing test procedures described in Section III, we are
updating regulatory useful life periods to further assure emission
performance of heavy-duty highway engines. In this section, we present
the updated regulatory useful life periods we are finalizing in this
rule. In Section IV.A.1, we present our revised useful life periods
that will apply for the new exhaust emission standards for criteria
pollutants, OBD, and requirements related to crankcase emissions. In
Section IV.A.2, we present the useful life periods that will apply for
the new refueling emission standards for certain Spark-ignition HDE. As
described in Section G.10 of this preamble, we are not finalizing the
proposed allowance for manufacturers to generate NOX
emissions credits from heavy-duty zero emissions vehicles (ZEVs) or the
associated useful life requirements.
1. Regulatory Useful Life Periods by Primary Intended Service Class
    In this final rule, we are increasing the regulatory useful life
mileage values for new heavy-duty engines to better reflect real-world
usage, extend the emissions durability requirement for heavy-duty
engines, and improve long-term emission performance. In this Section
IV.1, we describe the regulatory useful life periods we are finalizing
for the four primary intended service classes for heavy-duty highway
engines.\315\ Our longer useful life periods vary by engine class to
reflect the different lengths of their estimated operational lives. As
described in the proposal for this rule, we continue to consider
operational life to be the average mileage at rebuild for CI engines
and the average mileage at replacement for SI engines.\316\
---------------------------------------------------------------------------

    \315\ The useful life periods we are finalizing in this rule
apply for criteria pollutant standards; we did not propose and are
not finalizing changes to the useful life periods that apply for GHG
standards.
    \316\ See Chapter 2.4 of the RIA for a summary of the history of
our regulatory useful life provisions and our estimate of the
operational life for each heavy-duty engine class.
---------------------------------------------------------------------------

    In determining the appropriate longer useful life values to set in
the final rule, we retain our proposed objective to set useful life
periods that cover a significant portion of the engine's operational
life. However, as explained in the proposal, we also maintain that

the emission standards presented in Section III must be considered
together with their associated useful life periods. After further
consideration of the basis for the proposal, comments received,
supporting data available since the proposal, and the numeric level of
the final standards, we are selecting final useful life values within
the range of options proposed that cover a significant portion of the
engine's operational life and take into account the combined effect of
useful life and the final numeric standards on the overall stringency
and emissions reductions of the program. As described in the final RIA,
we concluded two engine test programs for this rule that demonstrated
technologies that are capable of meeting lower emission levels at much
longer mileages than current useful life periods. We evaluated a heavy-
duty diesel engine to a catalyst-aged equivalent of 800,000 miles for
the compression-ignition demonstration program, and a heavy-duty
gasoline engine to a catalyst-aged equivalent of 250,000 miles for the
spark-ignition demonstration program. As described in Section III of
this preamble, the results of those demonstration programs informed the
appropriate standard levels for the useful life periods we are
finalizing for each engine class. Our final useful life values were
also informed by comments, including additional information on
uncertainties and potential corresponding costs. We summarize key
comments in Section IV.1.ii, and provide complete responses to useful
life comments in section 3.8 of the Response to Comments document.
    Our final useful life periods for Spark-ignition HDE, Light HDE,
Medium HDE, and Heavy HDE classes are presented in Table IV-1 and
specified in a new 40 CFR 1036.104(e).\317\ The final useful life
values that apply for Spark-ignition HDE, Light HDE, and Medium HDE
starting in MY 2027 match the most stringent option we proposed, that
is, MY 2031 step of proposed Option 1. The final useful life values for
Heavy HDE, which has a distinctly longer operational life than the
smaller engine classes, match the longest useful life mileage we
proposed for model year 2027 (i.e., the Heavy HDE mileage of proposed
Option 2). We are also increasing the years-based useful life from the
current 10 years to values that vary by engine class and match the
proposed value in the respective proposed option. After considering
comments, we are also adding hours-based useful life values to all
primary intended service classes based on a 20 mile per hour speed
threshold and the corresponding final mileage values.
---------------------------------------------------------------------------

    \317\ We are migrating the current alternate standards for
engines used in certain specialty vehicles from 40 CFR 86.007-11 and
86.008-10 into 40 CFR 1036.605 without modification. See Section
XI.B of this preamble for a discussion of these standards.

                                         Table IV-1--Final Useful Life Periods by Primary Intended Service Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Current                                    MY 2027 and later
             Primary intended service class              -----------------------------------------------------------------------------------------------
                                                               Miles           Years           Hours           Miles           Years           Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spark-ignition HDE \a\..................................         110,000              10  ..............         200,000              15          10,000
Light HDE \a\...........................................         110,000              10  ..............         270,000              15          13,000
Medium HDE..............................................         185,000              10  ..............         350,000              12          17,000
Heavy HDE...............................................         435,000              10          22,000         650,000              11          32,000
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Current useful life period for Spark-ignition HDE and Light HDE for GHG emission standards is 15 years or 150,000 miles; we are not revising these
  useful life periods in this final rule. See 40 CFR 1036.108(d).

    For hybrid engines and powertrains, we are finalizing the proposal
that manufacturers certifying hybrid engines and powertrains would
declare the primary intended service class of their engine family using
40 CFR 1036.140. Once a primary intended service class is declared, the
engine configuration would be subject to the corresponding emission
standards and useful life values from 40 CFR 1036.104.
i. Summary of the Useful Life Proposal
    For CI engines, the proposed Option 1 useful life periods included
two steps in MYs 2027 and 2031 that aligned with the final useful life
periods of CARB's HD Omnibus regulation, and the proposed MY 2031
periods covered close to 80 percent of the expected operational life of
CI engines based on mileage at out-of-frame rebuild. The useful life
mileages of proposed Option 2, which was a single-step option starting
in MY 2027, generally corresponded to the average mileages at which CI
engines undergo the first in-frame rebuild. The rebuild data indicated
that CI engines can last well beyond the in-frame rebuild mileages. We
noted in the proposal that it was unlikely that we would finalize a
single step program with useful life mileages shorter than proposed
Option 2; instead, we signaled that we would likely adjust the numeric
value of the standards to address any feasibility concerns.
    For Spark-ignition HDE, the useful life mileage in proposed Option
1 was about 90 percent of the operational life of SI engines based on
mileage at replacement. The useful life of proposed Option 2 aligned
with the current SI engine useful life mileage that applies for GHG
standards. In the proposal, we noted that proposed Option 2 also
represented the lowest useful life mileage we would consider finalizing
for Spark-ignition HDE.
    In proposed Option 1, we increased the years-based useful life
values for all engine classes to account for engines that accumulate
fewer miles annually. We also proposed to update the hours-based useful
life criteria for the Heavy HDE class to account for engines that
operated frequently, but accumulated relatively few miles due to lower
vehicle speeds. We calculated the proposed hours values by applying the
same 20 mile per hour conversion factor to the proposed mileages as was
applied when calculating the useful life hours that currently apply for
Heavy HDE.\318\ The proposed hours specification was limited to the
Heavy HDE class to be consistent with current regulations, but we
requested comment on adding hours-based useful life values to apply for
the other service classes.
---------------------------------------------------------------------------

    \318\ U.S. EPA, ``Summary and Analysis of Comments: Control of
Emissions of Air Pollution from Highway Heavy-Duty Engines'', EPA-
420-R-97-102, September 1997, pp 43-47.
---------------------------------------------------------------------------

ii. Basis for the Final Useful Life Periods
    In this Section IV.1.ii, we provide the rationale for our final
useful life periods, including summaries and responses to certain
comments that informed our final program. The complete set of useful
life comments

and our responses are in section 3.8 of the Response to Comments
document. As explained in the NPRM, CAA section 202(d) provides that
the minimum useful life for heavy-duty vehicles and engines is a period
of 10 years or 100,000 miles, whichever occurs first, and further
authorizes EPA to adopt longer useful life periods that we determine to
be appropriate.
    Many commenters expressed general support for our proposal to
lengthen useful life periods in this rulemaking. Several commenters
expressed specific support for the useful life periods of proposed
Option 1 or proposed Option 2. Other commenters recommended EPA revise
the proposal to either lengthen or shorten the useful life periods to
values outside of the range of our proposed options.
    We are lengthening the current useful life mileages to capture the
greatest amount of the operational life for each engine class that we
have determined is appropriate at this time. We disagree with
commenters recommending that we finalize useful life periods below the
mileages of proposed Option 2. As noted in our proposal, proposed
Option 2 represented the lower bound of useful life mileages we would
consider finalizing for all engine classes. Furthermore, as described
in Section III of this preamble and Chapter 3 of the RIA for this final
rule, both of EPA's engine test programs successfully demonstrated that
CI and SI engine technologies can achieve low emission levels at
mileages (800,000 miles and 250,000 miles, respectively) well beyond
Option 2. Even after taking into consideration uncertainties of the
impacts of variability and real world operation on emission levels at
the longest mileages, the test programs' data supports that mileages at
least as long as Option 2 are appropriate, and the final standards are
feasible at those mileages. We also disagree with commenters suggesting
we finalize mileages longer than proposed Option 1. We did not propose
and for the reasons just explained about impacts on emission level at
the longest mileages do not believe it is appropriate at this time to
require useful life periods beyond proposed Option 1.
    Organizations submitting adverse comments on useful life focused
mostly on the useful life mileages proposed for the Heavy HDE service
class. Technology suppliers and engine manufacturers expressed concern
with the lack of data from engines at mileages well beyond the current
useful life. Suppliers commented that it could be costly and
challenging to design components without more information on component
durability, failure modes, and use patterns at high mileages. Engine
manufacturers claimed that some uncertainties relating to real world
use would limit the feasibility of the proposed Option 1 useful life
periods, including: The range of applications in which these engines
are used, variable operator behavior (including 2nd and 3rd owners),
and the use of new technology that is currently unproven in the field.
In Sections III and IV.F of this preamble, we describe other areas
where useful life plays a role and manufacturers expressed concern over
uncertainties, including certification, DF testing, engine rating
differences, lab-to-lab variability, production variability, and in-use
engine variability. Due to these combined uncertainties, manufacturers
stated that they expect to be conservative in their design and
maintenance strategies, and some may opt to schedule aftertreatment
replacement as a means to ensure compliance with new NOX
emission standards, particularly for proposed Option 1 numeric
standards and useful life values. Comments did not indicate a concern
that manufacturers may schedule aftertreatment replacement for the
smaller engine classes at the proposed Option 1 useful life periods.
    We agree that there are uncertainties associated with implementing
new technology to meet new emission standards, and recognize that the
uncertainties are highest for Heavy HDE that are expected to have the
longest operational life and useful life periods. We acknowledge that
higher useful life mileage is one factor that may contribute to a risk
that manufacturers would schedule aftertreatment replacement to ensure
compliance for the heaviest engine class. Specific to Heavy HDE, the
final useful life mileage of 650,000 miles matches the longest useful
life mileage we proposed for model year 2027 and we expect
manufacturers have experience with their engines at this mileage
through their extended warranty offerings, thus reducing uncertainties
of real world operation compared to the longest useful life mileage we
proposed (i.e., 800,000 miles).\319\ For Heavy HDE, the final numeric
emission standards and useful life periods matching proposed Option 2,
combined with other test procedure revisions to provide clarity and
address variability, will require less conservative compliance
strategies than proposed Option 1 and will not require manufacturers to
plan for the replacement of the entire catalyst system. See Section III
for further discussion on the basis and feasibility of the final
emission standards.
---------------------------------------------------------------------------

    \319\ Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-2019-
0055. ``Example Extended Warranty Packages for Heavy-duty Engines''.
September 29, 2022.
---------------------------------------------------------------------------

    Many commenters supported proposed Option 1, including useful life
periods out to 800,000 miles for the Heavy HDE class. Several
commenters pointed to EPA's engine testing results on an engine aged to
the equivalent of 800,000 miles as adequately demonstrating feasibility
of an 800,000-mile useful life for Heavy HDE. We agree that CI engines
are capable of meeting low emission levels at very high mileages in a
controlled laboratory environment, but manufacturer liability for
maintaining certified emission levels over the regulatory useful life
period is not restricted to laboratory tests. Manufacturers expressed
specific concern about the uncertainties outside the controlled
laboratory environment after an engine enters commerce. In Sections III
and IV.F of this preamble we summarize comments relating to how useful
life factors into certification, DF testing, and in-use testing. In
Section III.B, we describe a certification requirement we are
finalizing for manufacturers to demonstrate the emission controls on
Heavy HDE are durable through the equivalent of 750,000 miles; this
durability demonstration will extend beyond the 650,000 mile useful
life period for these engines. We expect this extended laboratory-based
demonstration, in a controlled environment, will translate to greater
assurance that an engine will maintain its certified emission levels in
real world operation where conditions are more variable throughout the
regulatory useful life. This greater assurance would be achieved while
minimizing the compliance uncertainties identified by manufacturers in
comments for the highest proposed useful life mileages.
    We believe manufacturers can adequately ensure the durability of
their smaller engines over useful life periods that match proposed
Option 1 both for meeting emission standards in the laboratory at
certification and in the laboratory and applicable in-use testing after
operation in the real world. The final durability demonstration
requirements for Spark-ignition HDE, Light HDE, and Medium HDE match
the final useful life periods for those smaller engines classes.
    As shown in Table IV-1, we are also finalizing useful life periods
in years and hours for all primary intended service classes. We are
updating the years values from the current 10 years to 15 years for
Spark-ignition HDE and

Light HDE, 12 years for Medium HDE, and 11 years for Heavy HDE. The
final years values match the years values we proposed and vary by
engine class corresponding to the proposed mileage option we are
finalizing. We are also adding hours as a useful life criteria for all
engine classes. We received no adverse comments for hours-based useful
life periods and are finalizing hours values by applying a 20-mph
conversion factor, as proposed, to calculate hours values from the
final mileage values.
    We have finalized a combination of emissions standards and useful
life values that our analysis and supporting data demonstrate are
feasible for all heavy-duty engine classes. We are lengthening the
existing useful life mileages to capture the greatest amount of the
operational life for each engine class that we have determined is
appropriate at this time, while considering the impact of useful life
length on the stringency of the standards and other requirements of
this final rule. Preamble Section III describes how our analysis and
the EPA engine test programs demonstrated feasibility of the standards
at these useful life values, including data on emission levels at the
equivalent useful life mileages.
2. Useful Life for Incomplete Vehicle Refueling Emission Standards
    As described in Section III.E., we are finalizing a refueling
emission standard for incomplete vehicles above 14,000 lb GVWR.
Manufacturers would meet the refueling emission standard by installing
onboard refueling vapor recovery (ORVR) systems on these incomplete
vehicles. Since ORVR systems are based on the same carbon canister
technology that manufacturers currently use to control evaporative
emissions on these incomplete vehicles, we proposed to align the useful
life periods for the two systems. In 40 CFR 1037.103(f), we are
finalizing a useful life of 15 years or 150,000 miles, whichever comes
first, for refueling standards for incomplete vehicles above 14,000 lb
GVWR, as proposed.
    Evaporative emission control systems are currently part of the fuel
system of incomplete vehicles, and manufacturers are meeting applicable
standards and useful life requirements for evaporative systems today.
ORVR is a mature technology that has been installed on complete
vehicles for many years, and incomplete vehicle manufacturers have
experience with ORVR systems through their complete vehicle
applications. Considering the manufacturers' experience with
evaporative emission standards for incomplete vehicles, and their
familiarity with ORVR systems, we continue to believe it would be
feasible for manufacturers to apply the same evaporative emission
standard useful life periods to refueling standards. We received no
adverse comments relating to the proposed 15 years/150,000 miles useful
life for refueling standards, and several manufacturers commented in
support of our proposed periods.

B. Ensuring Long-Term In-Use Emissions Performance

    In the proposal, we introduced several ideas for an enhanced,
comprehensive strategy to ensure in-use emissions performance over more
of an engine's operational life. In this section, we discuss the final
provisions to lengthen emission-related warranty periods, update
maintenance requirements, and improve serviceability in this rule.
Taken together, these updates are intended to increase the likelihood
that engine emission controls will be maintained properly through more
of the service life of heavy-duty engines and vehicles, including
beyond useful life.
1. Emission-Related Warranty
    The emission-related warranty period is the period over which CAA
section 207 requires an engine manufacturer to warrant to a purchaser
that the engine is designed, built, and equipped so as to conform with
applicable regulations under CAA section 202 and is free from defects
in materials or workmanship which would cause the engine not to conform
with applicable regulations for the warranty period. If an emission-
related component fails during the regulatory emission warranty period,
the manufacturer is required to pay for the cost of repair or
replacement. A manufacturer's general emissions warranty
responsibilities are currently set out in 40 CFR 1068.115. Note that
while an emission warranty provides protection to the owner against
emission-related repair costs during the warranty period, the owner is
responsible for properly maintaining the engine (40 CFR 1068.110(e)),
and the manufacturer may deny warranty claims for failures that have
been caused by the owner's or operator's improper maintenance or use
(40 CFR 1068.115(a)).
    In this section, we present the updated emission-related warranty
periods we are finalizing for heavy-duty highway engines and vehicles
included in this rule. As described in Section G.10 of this preamble,
we are not finalizing the proposed allowance for manufacturers to
generate NOX emissions credits from heavy-duty zero
emissions vehicles (ZEVs) or the associated warranty requirements.
i. Final Warranty Periods by Primary Intended Service Class
    We are updating and significantly strengthening our emission-
related warranty periods for model year 2027 and later heavy-duty
engines.\320\ We are finalizing most of the emission-related warranty
provisions of 40 CFR 1036.120 as proposed. Following our approach for
useful life, we are revising the proposed warranty periods for each
primary intended service class to reflect the difference in average
operational life of each class and after considering additional
information provided by commenters. See section 4 of the Response to
Comments document for our detailed responses, including descriptions of
revisions to the proposed regulatory text in response to commenter
requests for clarification.
---------------------------------------------------------------------------

    \320\ Emission-related components for only criteria pollutant
emissions or both greenhouse gas (i.e., CO2, N2O, and CH4) and
criteria pollutant emissions would be subject to the final warranty
periods of 40 CFR 1036.120. See 40 CFR 1036.150(w).
---------------------------------------------------------------------------

    EPA's current emissions-related warranty periods for heavy-duty
engines range from 22 percent to 54 percent of the current regulatory
useful life; the warranty periods have not changed since 1983 even as
the useful life periods were lengthened.\321\ The revised warranty
periods are expected to result in better engine maintenance and less
tampering, which would help to maintain the benefits of the emission
controls. In addition, longer regulatory warranty periods may lead
engine manufacturers to simplify repair processes and make them more
aware of system defects that need to be tracked and reported to EPA.
---------------------------------------------------------------------------

    \321\ The useful life for heavy heavy-duty engines was increased
from 290,000 miles to 435,000 miles for 2004 and later model years
(62 FR 54694, October 21, 1997).
---------------------------------------------------------------------------

    Our final emission-related warranty periods for heavy-duty engines
are presented in Table IV-2 and specified in a new 40 CFR
1036.120.322 323 The final warranty mileages that apply
starting in MY 2027 for Spark-ignition HDE, Light HDE, and Medium HDE
match the longest warranty mileages proposed (i.e., MY 2031 step of
proposed Option 1) for these primary intended service

classes. For Heavy HDE, the final warranty mileage matches the longest
warranty mileage proposed for MY 2027 (i.e., MY 2027 step of proposed
Option 1). We are also increasing the years-based warranty from the
current 5 years to 10 years for all engine classes. After considering
comments, we are also adding hours-based warranty values to all primary
intended service classes based on a 20 mile per hour speed threshold
and the corresponding final mileage values. Consistent with current
warranty provisions, the warranty period would be whichever warranty
value (i.e., mileage, hours, or years) occurs first. We summarize key
comments in Section IV.B.1.i.a, and provide complete responses to
warranty comments in section 4 of the Response to Comments document.
---------------------------------------------------------------------------

    \322\ All engines covered by a primary intended service class
would be subject to the corresponding warranty period, regardless of
fuel used.
    \323\ We are migrating the current alternate standards for
engines used in certain specialty vehicles from 40 CFR 86.007-11 and
86.008-10 into 40 CFR 1036.605 without modifying those alternate
standards, as proposed. See Section XI.B of this preamble for a
discussion of these standards.

                                  Table IV-2--Final Emission-Related Warranty Periods by Primary Intended Service Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Current                                Model year 2027 and later
             Primary intended service class              -----------------------------------------------------------------------------------------------
                                                              Mileage          Years           Hours          Mileage          Years           Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spark-Ignition HDE......................................          50,000               5  ..............         160,000              10           8,000
Light HDE...............................................          50,000               5  ..............         210,000              10          10,000
Medium HDE..............................................         100,000               5  ..............         280,000              10          14,000
Heavy HDE...............................................         100,000               5  ..............         450,000              10          22,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We note that we are finalizing as proposed that when a
manufacturer's certified configuration includes hybrid system
components (e.g., batteries, electric motors, and inverters), those
components are considered emission-related components, which would be
covered under the warranty requirements in new 40 CFR 1036.120.\324\
Similar to the approach for useful life in Section IV.A, a manufacturer
certifying a hybrid engine or hybrid powertrain would declare a primary
intended service class for the engine family and apply the
corresponding warranty periods in 40 CFR 1036.120 when certifying the
engine configuration.\325\ This approach to clarify that hybrid
components are part of the broader engine configuration provides
vehicle owners and operators with consistent warranty coverage based on
the intended vehicle application.
---------------------------------------------------------------------------

    \324\ See our new definition of ``emission-related component''
in 40 CFR 1036.801. Defects or failures of hybrid system components
can result in the engine operating more, and thus increase
emissions.
    \325\ As described in 40 CFR 1036.140, the primary intended
service classes are partially based on the GVWR of the vehicle in
which the configuration is intended to be used. See also the update
to definition of ``engine configuration'' in 40 CFR 1036.801 to
clarify that an engine configuration would include hybrid components
if it is certified as a hybrid engine or hybrid powertrain.
---------------------------------------------------------------------------

    We estimated the emissions impacts of the final warranty periods in
our inventory analysis, which is summarized in Section VI and discussed
in detail in Chapter 5 of our RIA. In Section V, we estimate costs
associated with the final warranty periods, including indirect costs
for manufacturers and operating costs for owners and operators.
a. Summary of the Emission-Related Warranty Proposal
    In the proposal, we included several justifications for lengthened
warranty periods that continue to apply for the final provisions.
First, we expected longer emission-related warranty periods would lead
owners to continue maintain their engines and vehicles over a longer
period of time and ensure longer-term benefits of emission
controls.\326\ Since emission-related repairs would be covered by
manufacturers for a longer period of time, an owner would be more
likely to have systems repaired and less likely to tamper to avoid the
cost of a repair.\327\
---------------------------------------------------------------------------

    \326\ See Chapter 5 of the RIA for a discussion of mal-
maintenance and tampering effects in our emission inventory
estimates.
    \327\ Existing warranty provisions specify that owners are
responsible for properly maintaining their engines (40 CFR
1068.110(e)) and manufacturers may deny warranty claims for failures
that have been caused by the owner's or operator's improper
maintenance or use (40 CFR 1068.115(a)). See Section IV.B.2 for a
description of updates to the allowable maintenance provisions.
---------------------------------------------------------------------------

    Second, emission-related repair processes may get more attention
from manufacturers if they are responsible for repairs over a longer
period of time. The current, relatively short warranty periods provide
little incentive for manufacturers to evaluate the complexity of their
repair processes, since the owner pays for the repairs after the
warranty period ends. As manufacturers try to remain competitive,
longer emission warranty periods may lead manufacturers to simplify
repair processes and provide better training to technicians in an
effort to reduce their warranty repair costs. Simplifying repair
processes could include modifying emission control components in terms
of how systems are serviced and how components are replaced (e.g.,
modular sub-assemblies that could be replaced individually, resulting
in a quicker, less expensive repair). Improved technician training may
also reduce warranty repair costs by improving identification and
diagnosing component failures more quickly and accurately, thus
reducing downtime for owners and avoiding repeated failures,
misdiagnoses of failures, and higher costs from repeat repair events at
service facilities.
    Finally, longer regulatory emission warranty periods would increase
the period over which the engine manufacturer would be made aware of
emission-related defects. Manufacturers are currently required to track
and report defects to the Agency under the defect reporting provisions
of 40 CFR part 1068. Under 40 CFR 1068.501(b), manufacturers
investigate possible defects whenever a warranty claim is submitted for
a component. Therefore, manufacturers can easily monitor defect
information from dealers and repair shops who are performing those
warranty repair services, but after the warranty period ends, the
manufacturer would not necessarily know about these events, since
repair facilities are less likely to be in contact with the
manufacturers and they are less likely to use OEM parts. A longer
warranty period would allow manufacturers to have access to better
defect information over a period of time more consistent with engine
useful life.
    In the proposal, we also highlighted that a longer warranty period
would encourage owners of vehicles powered by SI engines (as for CI
engines) to follow manufacturer-prescribed maintenance procedures for a
longer period of time, as failure to do so would void the warranty. We
noted that the impact of a longer emissions warranty period may be
slightly different for SI engines from a tampering perspective. Spark-
ignition engine systems rely on mature technologies, including
evaporative emission systems and three-way catalyst-based emission
controls, that have been consistently reliable for light-duty and
heavy-duty vehicle

owners.\328\ SI engine owners may not currently be motivated to tamper
with their catalyst systems to avoid repairs, but they may purchase
defeat devices intended to disable emission controls to boost the
performance of their engines. We expected SI engine owners may be less
inclined to install such defeat devices during a longer warranty
period.
---------------------------------------------------------------------------

    \328\ The last U.S. EPA enforcement action against a
manufacturer for three-way catalysts was settled with
DaimlerChrylser Corporation Settlement on December 21, 2005.
Available online: https://www.epa.gov/enforcement/daimlerchrysler-corporation-settlement.
---------------------------------------------------------------------------

    We proposed two options that generally represented the range of
revised emission warranty periods we considered adopting in the final
rule. Proposed Option 1 included warranty periods that aligned with the
MY 2027 and MY 2031 periods of the CARB HD Omnibus program and were
close to 80 percent of useful life. At the time of the proposal, we
assumed most manufacturers would continue to certify 50-state compliant
engines in MY 2027 and later, and it would simplify the certification
process if there would be consistency between CARB and Federal
requirements. The warranty periods of proposed Option 2 were proposed
to apply in a single step beginning in model year 2027 and to match
CARB's Step 1 warranty periods for engines sold in California.\329\ The
proposed Option 2 mileages covered 40 to 55 percent of the proposed
Option 1 MY 2031 useful life mileages and represented an appropriate
lower end of the range of the revised regulatory emission warranty
periods we considered.
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    \329\ Since the CARB Step 1 warranty program did not include
updates to warranty for SI engines, the proposed Option 2 warranty
mileage for that the Spark-ignition HDE class matched the current
useful life for those engines, consistent with the approach for
Light HDE proposed Option 2 warranty.
---------------------------------------------------------------------------

    While we noted that a majority of engines would reach the warranty
mileage in a reasonable amount of time, some applications may have very
low annual mileage due to infrequent use or low speed operation and may
not reach the warranty mileage for many years. To ensure manufacturers
are not indefinitely responsible for components covered under emissions
warranty in these situations, we proposed to revise the years-based
warranty periods and proposed hours-based warranty periods for all
engine classes in proposed Option 1.
    For the years-based period, which would likely be reached first by
engines with lower annual mileage due to infrequent use, we proposed to
increase the current period from 5 years to 7 years for MY 2027 through
2030, and to 10 years starting with MY 2031. We also proposed to add an
hours-based warranty period to cover engines that operate at low speed
and/or are frequently in idle mode.\330\ In contrast to infrequent use,
low speed and frequent idle operation can strain emission control
components. We proposed an hours-based warranty period to allow
manufacturers to factor gradually-accumulated work into their warranty
obligations.
---------------------------------------------------------------------------

    \330\ We proposed warranty hours for all primary intended
service classes based on a 20 mile per hour average vehicle speed
threshold to convert from the proposed mileage values.
---------------------------------------------------------------------------

b. Basis for the Final Emission-Related Warranty Periods
    As detailed in section 4 of the Response to Comments document for
this rule, commenter support for lengthening emission-related warranty
periods varied. Many commenters expressed general support for our
proposal to lengthen warranty periods in this rulemaking. Several
commenters expressed specific support for the warranty periods of
proposed Option 1 or proposed Option 2. Other commenters recommended
EPA revise the proposal to either lengthen or shorten the warranty
periods to values outside of the range of our proposed options.
    Our final warranty periods continue to be influenced by the
potential beneficial outcomes of lengthening emission-related warranty
periods that we discussed in the proposal. Specifically, we continue to
believe lengthened warranty periods will effectively assure owners
properly maintain and repair their emission controls over a longer
period, reduce the likelihood of tampering, provide additional
information on failure modes, and create a greater incentive for
manufacturers to simplify repair processes to reduce costs. Several
commenters agreed with our list of potential outcomes, with some noting
that any associated emissions benefits would be accelerated by pulling
ahead the warranty periods of the MY 2031 step of proposed Option 1 to
begin in MY 2027.
    Organizations submitting adverse comments on lengthening warranty
periods focused mostly the warranty mileages proposed for the Heavy HDE
service class. Technology suppliers and engine manufacturers expressed
concern with the lack of data from engines at high mileages, including
uncertainties related to frequency and cause of failures, varying
vehicle applications, and operational changes as the engine ages. We
considered commenters' concerns regarding how uncertainties for the
highest mileages of proposed Option 1 could cause manufacturers to
respond by conservatively estimating their warranty cost. We continue
to expect, as noted in the proposal, that manufacturers are likely to
recoup the costs of warranty by increasing the purchase price of their
products. We agree with comments indicating that increases in purchase
price can increase the risk of pre-buy or low-buy, especially for the
heaviest engine class, Heavy HDE.
    As described in this section, the final warranty periods are within
the range of periods over which we expect manufacturers have access to
failure data, which should limit the need for manufacturers to
conservatively estimate warranty costs. We summarize our updated cost
and economic impact analyses, which reflect the final warranty periods,
in Sections V and X of this preamble, respectively. For more
information, see our complete assessments of costs in Chapter 7 and
economic impacts in Chapter 10 of the Regulatory Impact Analysis for
this final rule.
    We retain our proposed objectives to lengthen warranty periods to
cover a larger portion of the operational lives and to be more
consistent with the final useful life periods. Similar to our approach
for the useful life mileages in this final rule (see Section IV.A of
this preamble), we believe it is appropriate to pull ahead the longest
proposed MY 2031 warranty periods to apply in MY 2027 for the smaller
engine classes. For Spark-ignition HDE, Light HDE, and Medium HDE, the
final warranty mileages are 160,000 miles, 210,000 miles, and 280,000
miles, respectively, which cover about 80 percent of the corresponding
final useful life mileages. In response to commenters concerned with
data limitations, we expect any component failure and wear data
available from engines in the largest engine class would be applicable
to the smaller engine classes. As such, manufacturers and suppliers
have access to failure and wear data at the mileages we are finalizing
for the smaller engine classes through their current R&D and in-use
programs evaluating components for larger engines that currently have a
435,000 mile useful life.
    We are not applying the same pull-ahead approach for the Heavy HDE
warranty mileage. We do not believe it is appropriate at this time to
finalize a 600,000-mile warranty for the Heavy HDE class that would
uniquely cover greater than 90 percent of the 650,000-

mile final useful life, especially considering the comments pointing to
uncertainties, lack of data, and potential high costs specific to Heavy
HDE. We are also not applying the approach of adopting the warranty
mileage of proposed Option 2, as was done for Heavy HDE useful life, as
we do not believe the proposed Option 2 warranty of 350,000 miles would
provide emission control assurance over a sufficient portion of the
useful life. Instead, we are finalizing a warranty mileage that matches
the longest mileage proposed for MY 2027 (450,000 miles), covering a
percentage of the final useful life that is more consistent with the
warranty periods of the smaller engine classes. The final warranty
mileage for Heavy HDE is only 15,000 miles longer than the current
useful life for this engine class. As noted for the warranties of the
smaller engine classes, we expect manufacturers and suppliers have
access to failure data nearing 450,000 miles through their R&D programs
evaluating Heavy HDE over their current useful life. We expect
manufacturers also have experience with their engines at this mileage
through their extended warranty offerings; thus, they already possess
real world operational data in addition to their internal
evaluations.\331\
---------------------------------------------------------------------------

    \331\ Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-2019-
0055. ``Example Extended Warranty Packages for Heavy-duty Engines''.
September 29, 2022.
---------------------------------------------------------------------------

    Several organizations commented on the proposed years or hours
criteria for warranty. One supplier noted that analyses focused on
tractors and their relatively high mileages may not accurately predict
the use of vocational vehicles that are more limited by hours of
operation. The same supplier suggested EPA should further differentiate
warranties by vehicles classes and vocations. Another organization
cautioned against warranty periods that are one-size-fits-all. Two
organizations supported applying an hours-based warranty period for all
engine classes to cover lower-speed applications and the 20-mph
conversion factor that we proposed.
    We agree that vocational vehicles have distinct use patterns;
however, we did not propose and are not finalizing warranty periods at
the vehicle level to distinguish between vehicle types in this rule. We
are finalizing three warranty thresholds for each heavy-duty engine
class: A mileage threshold that is likely to reached first by vehicles
driving many miles annually, a years threshold that is likely to be
reached first by vehicles that drive infrequently or seasonally, and an
hours threshold that is likely to be reached first by vehicles that
drive frequently at lower speeds or with significant idling. We believe
adding an hours threshold in the final rule to the mileage- and years-
based warranty periods for all engine classes will lead to more
equitable warranty obligations across the range of possible vehicle
applications for which a heavy-duty engine may be used.
ii. Warranty for Incomplete Vehicle Refueling Emission Controls
    As noted in Section III.E, we are finalizing refueling emission
standards for Spark-ignition HDE that are certified as incomplete
vehicles above 14,000 lb GVWR.\332\ Our refueling standards are
equivalent to the refueling standards that are in effect for light- and
heavy-duty complete Spark-ignition HDVs. We project manufacturers would
meet the new refueling standards by adapting the existing onboard
refueling vapor recovery (ORVR) systems from systems designed for
complete vehicles. The new ORVR systems will likely supplement existing
evaporative emission control systems installed on these vehicles.
---------------------------------------------------------------------------

    \332\ See the final updates to 40 CFR 1037.103.
---------------------------------------------------------------------------

    We are finalizing warranty periods for the ORVR systems of
incomplete vehicles above 14,000 lb GVWR that align with the current
warranty periods for the evaporative systems on those vehicles.
Specifically, warranty periods for refueling emission controls would be
5 years or 50,000 miles on incomplete Light HDV, and 5 years or 100,000
miles on incomplete Medium HDV and Heavy HDV, as proposed. See our
final updates to 40 CFR 1037.120. Our approach to apply the existing
warranty periods for evaporative emission control systems to the ORVR
systems is similar to our approach to the final regulatory useful life
periods associated with our final refueling standards discussed in
Section IV.A. We received no adverse comments on our proposed warranty
periods for refueling emission controls.
2. Maintenance
    In this section, we describe the migrated and updated maintenance
provisions we are finalizing for heavy-duty highway engines. Section
IV.F of this preamble summarizes the current durability demonstration
requirements and our final updates.
    Our final maintenance provisions, in a new section 40 CFR 1036.125,
combine and amend the existing criteria pollutant maintenance
provisions from 40 CFR 86.004-25 and 86.010-38. Similar to other part
1036 sections we are adding in this rule, the structure of the new 40
CFR 1036.125 is consistent with the maintenance sections in the
standard-setting parts of other sectors (e.g., nonroad compression-
ignition engines in 40 CFR 1039.125). In 40 CFR 1036.205(i), we are
codifying the current manufacturer practice of including maintenance
instructions in their application for certification such that approval
of those instructions would be part of a manufacturer's certification
process.\333\ We are also finalizing a new paragraph 40 CFR 1036.125(h)
outlining several owner's manual requirements, including migrated and
updated provisions from 40 CFR 86.010-38(a).
---------------------------------------------------------------------------

    \333\ The current submission of maintenance instructions
provisions in 40 CFR 86.079-39 are migrated into the requirements
for an application for certification provisions in 40 CFR 1036.205.
---------------------------------------------------------------------------

    This section summarizes the final provisions that clarify the types
of maintenance, update the options for demonstrating critical emission-
related maintenance will occur and the minimum scheduled maintenance
intervals for certain components, and specify the requirements for
maintenance instructions. The proposed rule provided an extensive
discussion of the rationale and information supporting the proposed
maintenance provisions (87 FR 17520, March 28, 2022). See also section
6 of the Response to Comments for a detailed discussion of the comments
and how they may have informed changes we are making to the proposal in
this final rule.
i. Types of Maintenance
    The new 40 CFR 1036.125 clarifies that maintenance includes any
inspection, adjustment, cleaning, repair, or replacement of components
and, consistent with 40 CFR 86.004-25(a)(2), broadly classifies
maintenance as emission-related or non-emission-related and scheduled
or unscheduled.\334\ As proposed, we are finalizing five types of
maintenance that manufacturers may choose to schedule: Critical
emission-related maintenance, recommended additional maintenance,
special maintenance, noncritical emission-related maintenance, and non-
emission-related maintenance. As we explained in the proposal,
identifying and defining these maintenance categories in final 40 CFR
1036.125 distinguishes between the types of maintenance manufacturers
may choose to recommend to owners in

maintenance instructions, identifies the requirements that apply to
maintenance performed during certification durability demonstrations,
and clarifies the relationship between the different types of
maintenance, emissions warranty requirements, and in-use testing
requirements. The final provisions thus also specify the conditions for
scheduling each of these five maintenance categories.
---------------------------------------------------------------------------

    \334\ We include repairs as a part of maintenance because proper
maintenance would require owners to repair failed or malfunctioning
components. We note that repairs are considered unscheduled
maintenance that would not be performed during durability testing
and may be covered under warranty.
---------------------------------------------------------------------------

    We summarize several revisions to the proposed critical emission-
related maintenance provisions in Section 0 with additional details in
section 6 of the Response to Comments document. As proposed, the four
other types of maintenance will require varying levels of EPA approval.
In 40 CFR 1036.125(b), we propose to define recommended additional
maintenance as maintenance that manufacturers recommend owners perform
for critical emission-related components in addition to what is
approved for those components under 40 CFR 1036.125(a). We are
finalizing this provision as proposed except for a clarification in
wording to connect additional recommended maintenance and critical
emission-related maintenance more clearly. Under the final provisions,
a manufacturer may recommend that owners replace a critical emission-
related component at a shorter interval than the manufacturer received
approval to schedule for critical emission-related maintenance;
however, the manufacturer will have to clearly distinguish their
recommended intervals from the critical emission-related scheduled
maintenance in their maintenance instructions. As described in this
Section III.B.2 and the proposal, recommended additional maintenance is
not performed in the durability demonstration and cannot be used to
deny a warranty claim, so manufacturers will not be limited by the
minimum maintenance intervals or need the same approval from EPA by
demonstrating the maintenance would occur.
    In 40 CFR 1036.125(c), we proposed that special maintenance would
be more frequent maintenance approved at shorter intervals to address
special situations, such as atypical engine operation. We received one
comment requesting we clarify special maintenance in proposed 40 CFR
1036.125(c) and we are finalizing this provision as proposed except
that we are including an example of biodiesel use in the final
paragraph (c). Under the final provisions, manufacturers will clearly
state that the maintenance is associated with a special situation in
the maintenance instructions provided to EPA and owners.
    In 40 CFR 1036.125(d), as proposed, we are finalizing that
noncritical emission-related maintenance includes inspections and
maintenance that is performed on emission-related components but is
considered ``noncritical'' because emission control will be unaffected
(consistent with existing 40 CFR 86.010-38(d)). Under this final
provision, manufacturers may recommend noncritical emission-related
inspections and maintenance in their maintenance instructions if they
clearly state that it is not required to maintain the emissions
warranty.
    In 40 CFR 1036.125(e), we are updating the paragraph heading from
nonemission-related maintenance to maintenance that is not emission-
related to be consistent with other sectors. The final provision, as
proposed, describes the maintenance as unrelated to emission controls
(e.g., oil changes) and states that manufacturers' maintenance
instructions can include any amount of maintenance unrelated to
emission controls that is needed for proper functioning of the engine.
Critical Emission-Related Components
    Consistent with the existing and proposed maintenance provisions,
the final provisions continue to distinguish certain components as
critical emission-related components. The proposal did not migrate the
specific list of components defined as ``critical emission-related
components'' from 40 CFR 86.004-25(b)(6)(i); instead, we proposed and
are finalizing that manufacturers identify their specific critical
components by obtaining EPA's approval for critical emission-related
maintenance using 40 CFR 1036.125(a). Separately, we also proposed a
new definition for critical emission-related components in 40 CFR
1068.30 and are finalizing with revision. The final definition is
consistent with paragraph 40 CFR 86.004-25(b)(6)(i)(I) and the current
paragraph IV of 40 CFR part 1068, appendix A, as proposed.\335\ We are
removing the proposed reference to 40 CFR 1068, appendix A, in the
final definition, since appendix A specifies emission-related
components more generally. To avoid having similar text in two
locations, we are also replacing the current text of paragraph IV of 40
CFR 1068, appendix A, with a reference to the new part 1068 definition
of critical emission-related components.
---------------------------------------------------------------------------

    \335\ Paragraph (b)(6)(i)(I) concludes the list of critical
emission-related components in 40 CFR 86.004-25 with a general
description stating: ``Any other component whose primary purpose is
to reduce emissions or whose failure would commonly increase
emissions of any regulated pollutant without significantly degrading
engine performance.'' The existing paragraph (IV) of 40 CFR 1068,
appendix A similarly states: ``Emission-related components also
include any other part whose primary purpose is to reduce emissions
or whose failure would commonly increase emissions without
significantly degrading engine/equipment performance.''
---------------------------------------------------------------------------

ii. Critical Emission-Related Maintenance
    A primary focus of the final maintenance provisions is critical
emission-related maintenance. Critical emission-related maintenance
includes any adjustment, cleaning, repair, or replacement of emission-
related components that manufacturers identify as having a critical
role in the emission control of their engines. The final 40 CFR
1036.125(a), consistent with current maintenance provisions in 40 CFR
part 86 and the proposal, will continue to allow manufacturers to seek
advance approval from EPA for new emission-related maintenance they
wish to include in maintenance instructions and perform during
durability demonstration. The final 40 CFR 1036.125(a) retains the same
proposed structure that includes a maintenance demonstration and
minimum maintenance intervals, and a pathway for new technology that
may be applied in engines after model year 2020.
    We are finalizing with revision the maintenance demonstration
proposed in 40 CFR 1036.125(a)(1). The final provision includes the
five proposed options for manufacturers to demonstrate the maintenance
is reasonably likely to be performed in-use, with several clarifying
edits detailed in the Response to Comments document .\336\ As further
discussed in Section IV.D, we are finalizing the separate statement in
40 CFR 1036.125(a)(1) that points to the final inducement provisions,
noting that we will accept DEF replenishment as reasonably likely to
occur if an engine meets the specifications in proposed 40 CFR
1036.111; we are not setting a minimum maintenance interval for DEF
replenishment. Also, as noted in the proposal and reiterated here, the
first maintenance demonstration option, described in 40 CFR
1036.125(a)(1)(i), is intended to cover emission control technologies
that have an inherent performance degradation that coincides with
emission increases, such as back pressure resulting from a clogged DPF.
---------------------------------------------------------------------------

    \336\ The five maintenance demonstration options are consistent
with current maintenance demonstration requirements in 40 CFR
86.004-25 and 86.094-25.
---------------------------------------------------------------------------

    Consistent with the current and proposed maintenance provisions, we
are specifying minimum maintenance

intervals for certain emission-related components, such that
manufacturers may not schedule more frequent maintenance than we allow.
In 40 CFR 1036.125(a)(2), we are updating the list of components with
minimum maintenance intervals to more accurately reflect components in
use today and extending the replacement intervals such that they
reflect replacement intervals currently scheduled for those components.
See the NPRM preamble for a discussion of our justification for
terminology changes we are applying in the final rule, and the list of
components that we are not migrating from 40 CFR part 86 because they
are obsolete or covered by other parts.
    Consistent with current maintenance provisions, we proposed to
disallow replacement of catalyst beds and particulate filter elements
within the regulatory useful life of the engine.\337\ We are removing
reference to catalyst beds and particular filter elements in the
introductory text of paragraph (a)(2) and instead are adding them, with
updated terminology, as a separate line in the list of components in
Table 1 of 40 CFR 1036.125(a)(2) with minimum maintenance intervals
matching the final useful life values of this rule.\338\ Including
catalyst substrates and particulate filter substrates directly in the
table of minimum maintenance intervals more clearly connects the
intervals to the useful life values. In response to manufacturer
comments requesting clarification, we are also adding a reference to 40
CFR 1036.125(g) in paragraph (a)(2) to clarify that manufacturers are
not restricted from scheduling maintenance more frequent than the
minimum intervals, including replacement of catalyst substrates and
particulate filter substrates, if they pay for it.
---------------------------------------------------------------------------

    \337\ Existing 40 CFR 86.004-25(b)(4)(iii) states that only
adjustment and cleaning are allowed for catalyst beds and
particulate filter elements and that replacement is not allowed
during the useful life. Existing 40 CFR 86.004 25(i) clarifies that
these components could be replaced or repaired if manufacturers
demonstrate the maintenance will occur and the manufacturer pays for
it.
    \338\ In the final provision, we replaced ``catalyst bed'' with
``catalyst substrate'' and ``particulate filter element'' with
``particulate filter substrate''.
---------------------------------------------------------------------------

    We are finalizing as proposed the addition of minimum intervals for
replacing hybrid system components in engine configurations certified
as hybrid engines or hybrid powertrains, which would include the
rechargeable energy storage system (RESS). Our final minimum intervals
for hybrid system components equal the current useful life for the
primary intended service classes of the engines that these electric
power systems are intended to supplement or replace.\339\
---------------------------------------------------------------------------

    \339\ We note that Table IV-3 and the corresponding Table 1 of
40 CFR 1036.125(a)(2) include a reference to ``hybrid system
components'', which we inadvertently omitted from the tables in the
proposed rule.
---------------------------------------------------------------------------

    Table IV-3 summarizes the minimum replacement intervals we are
finalizing in a new table in 40 CFR 1036.125(a)(2). As explained in the
proposal, we believe it is appropriate to account for replacement
intervals that manufacturers have already identified and demonstrated
will occur for these components and the final replacement intervals
generally match the shortest mileage interval (i.e., most frequent
maintenance) of the published values, with some adjustments after
considering comments. Commenters noted that some sensors are not
integrated with a listed system and requested EPA retain a discrete set
of minimum intervals for sensors, actuators, and related ECMs. We agree
and are specifying minimum intervals that match the current intervals
for sensors, actuators, and related control modules that are not
integrated into other systems. We are retaining the proposed text to
indicate that intervals specified for a given system would apply for
all to actuators, sensors, tubing, valves, and wiring associated with
that component associated with that system. We are also revising the
minimum intervals for ignition wires from the proposed 100,000 miles to
50,000 miles to match the current intervals and adding an interval for
ignition coils at the same 50,000 miles after considering comments. See
section 6 of the Response to Comments document for other comments we
considered when developing the final maintenance provisions.
    We proposed to retain the maintenance intervals specified in 40 CFR
86.004-25 for adjusting or cleaning components as part of critical
emission-related maintenance. We are finalizing the proposed
maintenance intervals for adjusting and cleaning with one correction.
Commenters noted that the proposal omitted an initial minimum interval
for adjusting or cleaning EGR system components. Consistent with 40 CFR
86.004-25(b), we are correcting the proposed intervals for several
components (catalyst system components, EGR system components (other
than filters or coolers), particulate filtration system components, and
turbochargers) from 150,000 miles or 4,500 hours to include an initial
interval of 100,000 miles or 3,000 hours, with subsequent intervals of
150,000 miles or 4,500 hours. We did not reproduce the new Table 2 from
40 CFR 1036.125(a)(2) showing the minimum intervals for adjusting or
cleaning components in this preamble.

 Table IV-3--Minimum Scheduled Maintenance Intervals in Miles (or Hours) for Replacing Critical Emission-Related
                                          Components in 40 CR 1036.125
----------------------------------------------------------------------------------------------------------------
                                           Spark-ignition
               Components                        HDE            Light HDE        Medium HDE         Heavy HDE
----------------------------------------------------------------------------------------------------------------
Spark plugs.............................      25,000 (750)  ................  ................  ................
DEF filters.............................  ................   100,000 (3,000)   100,000 (3,000)   100,000 (3,000)
Crankcase ventilation valves and filters    60,000 (1,800)    60,000 (1,800)    60,000 (1,800)    60,000 (1,800)
 .......................................
Ignition wires and coils................    50,000 (1,500)  ................  ................  ................
Oxygen sensors..........................    80,000 (2,400)  ................  ................  ................
Air injection system components.........   110,000 (3,300)  ................  ................  ................
Sensors, actuators, and related control    100,000 (3,000)   100,000 (3,000)   150,000 (4,500)   150,000 (4,500)
 modules that are not integrated into
 other systems..........................
Particulate filtration systems (other      100,000 (3,000)   100,000 (3,000)   250,000 (7,500)   250,000 (7,500)
 than filter substrates)................
Catalyst systems (other than catalyst      110,000 (3,300)   110,000 (3,300)   185,000 (5,550)  435,000 (13,050)
 substrates), fuel injectors, electronic
 control modules, hybrid system
 components, turbochargers, and EGR
 system components (including filters
 and coolers)...........................
Catalyst substrates and particulate       200,000 (10,000)  270,000 (13,000)  350,000 (17,000)  650,000 (32,000)
 filter substrates......................
----------------------------------------------------------------------------------------------------------------

    We received no adverse comments on the proposed approach to
calculate the corresponding hours values for each minimum maintenance
interval. Consistent with our current maintenance provisions and the
proposal, we are finalizing minimum hours values based on the final
mileage and a 33 miles per hour vehicle speed (e.g., 150,000 miles
would equate to 4,500 hours).\340\ Consistent with the current
maintenance intervals specified in part 86 and the proposal, we are not
including year-based minimum intervals; OEMs can use good engineering
judgment if they choose to include a scheduled maintenance interval
based on years in their owner's manuals.
---------------------------------------------------------------------------

    \340\ The minimum hours-based intervals for catalyst substrates
and particulate filter substrates match the useful life hours that
apply for each primary intended service class to ensure these
components are not replaced within the regulatory useful life of the
engine, consistent with existing maintenance provisions. The useful
life hours are calculated using a 22 miles per hour conversion
factor as described in Section IV.A of this preamble.
---------------------------------------------------------------------------

    For new technology, not used on engines before model year 2020, we
are providing a process for manufacturers to seek approval for new
scheduled maintenance, consistent with the current maintenance
provisions. We received no adverse comment on the proposal to migrate
40 CFR 86.094-25(b)(7)(ii), which specifies a process for approval of
new critical emission-related maintenance associated with new
technology, and 40 CFR 86.094-25(b)(7)(iii), which allows manufacturers
to ask for a hearing if they object to our decision.\341\ We are
finalizing a new 40 CFR 1036.125(a)(3), as proposed.
---------------------------------------------------------------------------

    \341\ Hearing procedures are specified in 40 CFR 1036.820 and 40
CFR part 1068, subpart G.
---------------------------------------------------------------------------

iii. Source of Parts and Repairs
    Consistent with CAA section 207 \342\ and our existing regulations
for heavy duty vehicles under part 1037, we proposed a new paragraph 40
CFR 1036.125(f) to clarify that manufacturers' written instructions for
proper maintenance and use, discussed further in Section IV.B.2.vi,
generally cannot limit the source of parts and service owners use for
maintenance unless the component or service is provided without charge
under the purchase agreement, with two specified exceptions.\343\ We
are moving, with revisions, the content of the proposed paragraph (f)
to 40 CFR 1036.125(h)(2). See section 6 of the Response to Comments.
Consistent with the proposal, we are finalizing that manufacturers
cannot specify a particular brand, trade, or corporate name for
components or service and cannot deny a warranty claim due to
``improper maintenance'' based on owners choosing not to use a
franchised dealer or service facility or a specific brand of part
unless the component or service is provided without charge under the
purchase agreement. Consistent with current maintenance provisions and
CAA section 207(c)(3)(B), a second exception is that manufacturers can
specify a particular service facility and brand of parts only if the
manufacturer convinces EPA during the approval process that the engine
will only work properly with the identified service or component. We
are not finalizing at this time the proposed 40 CFR 1036.125(f)
requirement regarding specific statements on the first page of written
maintenance instructions; after consideration of comments, we agree
with commenters that the final regulatory text accomplishes the intent
of our proposal without the additional proposed first sentence.
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    \342\ See, e.g., CAA section 207(c)(3)(B) and (g).
    \343\ This provision has been adopted in the standard-setting
parts of several other sectors (see 1037.125(f)).
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iv. Payment for Scheduled Maintenance
    We proposed 40 CFR 1036.125(g) to allow manufacturers to schedule
maintenance not otherwise allowed by 40 CFR 1036.125(a)(2) if they pay
for it. The proposed paragraph (g) also included four criteria to
identify components for which we would require manufacturers to pay for
any scheduled maintenance within the regulatory useful life. The four
criteria, which are based on current provisions that apply for nonroad
compression-ignition engines, would require manufacturers to pay for
components that were not in general use on similar engines before 1980,
whose primary purpose is to reduce emissions, where the cost of the
scheduled maintenance is more than 2 percent of the price of the
engine, and where failure to perform the scheduled maintenance would
not significantly degrade engine performance.\344\ We continue to
believe that components meeting the four criteria are less likely to be
maintained without the incentive of manufacturers paying for it and we
are finalizing 40 CFR 1036.125(g) as proposed.
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    \344\ See 40 CFR 1039.125(g).
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    As noted in Section IV.B.2.ii, manufacturers cannot schedule
replacement of catalyst substrates or particulate filter substrates
within the regulatory useful life of the engine unless they pay for it.
As explained in the proposed rule, in addition to catalyst substrates
and particulate filter substrates, we expect that replacement of EGR
valves, EGR coolers, and RESS of certain hybrid systems also meet the
40 CFR 1036.125(g) criteria and manufacturers will only be able to
schedule replacement of these components if the manufacturer pays for
it.
    In the proposal, we requested comment on restricting the
replacement of turbochargers irrespective of the four criteria of
proposed 40 CFR 1036.125(g). One commenter suggested that EPA should
follow the CARB approach that requires manufacturers to pay for
scheduled maintenance of turbochargers within the regulatory useful
life. The comment indicated the cost of repairs and ``significant
impact'' of a failed turbocharger on emissions justify requiring that
manufacturers pay for replacement. We disagree and are not finalizing a
separate requirement for turbochargers. Turbochargers are not added to
engines specifically to control emissions and we expect the performance
degredation associated with a failing turbocharger is likely to
motivate owners to fix the problem. We continue to believe the four
criteria in 40 CFR 1036.125(g) are an appropriate means of
distinguishing components for which manufacturers should pay in order
to ensure the components are maintained.
v. Maintenance Instructions
    As proposed, our final 40 CFR 1036.125 preserves the requirement
that the manufacturer provide written instructions for properly
maintaining and using the engine and emission control system,
consistent with CAA section 207(c)(3)(A).\345\ The new 40 CFR
1036.125(h) describes the information that we are requiring
manufacturers to include in an owner's manual, consistent with CAA
sections 202 and 207. The new 40 CFR 1036.125(h)(1) generally migrates
the existing maintenance instruction provisions specified in 40 CFR
86.010-38(a). As described in Section IV.B.2.iii, final 40 CFR
1036.125(h)(2) includes revised content from proposed 40 CFR
1036.125(f). The final paragraph (h)(2) is also revised from the
proposed regulatory text to clarify that EPA did not intend the
proposed paragraph as a requirement for owners to maintain

records in order to make a warranty claim. While 40 CFR 1036.120(d)
allows manufacturers to deny warranty claims for improper maintenance
and use, owners have expressed concern that it is unclear what
recordkeeping is needed to document proper maintenance and use, and
both the proposed and final 40 CFR 1036.125(h)(2) are intended to
ensure manufacturers are communicating their expectations to owners.
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    \345\ CAA section 207(c)(3)(A) states that the manufacturer
shall furnish with each new motor vehicle or motor vehicle engine
written instructions for the proper maintenance and use of the
vehicle or engine by the ultimate purchaser and that such
instructions shall correspond to regulations which the Administrator
shall promulgate.
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    Consistent with the current 40 CFR 86.010-38(a)(2), our final 40
CFR 1036.125(h)(2) also requires manufacturers to describe in the
owner's manual if manufacturers expect owners to maintain any
documentation to show the engine and emission control system have been
properly maintained and, if so, to specify what documentation.
Manufacturers should be able to identify their expectations for
documenting routine maintenance and repairs related to warranty claims.
For instance, if a manufacturer requires a maintenance log as part of
their process for reviewing warranty claims and determining whether the
engine was properly maintained, we expect the owner's manual would
provide an example log with a clear statement that warranty claims
require an up-to-date maintenance record. We note that 40 CFR 1036.125
specifies minimum maintenance intervals for critical emission-related
maintenance, and limits manufacturers from invalidating warranty if
certain other types of allowable maintenance are not performed (i.e.,
recommended additional maintenance and noncritical emission-related
maintenance). Any required maintenance tasks and intervals must be
consistent with the requirements and limitations in 40 CFR 1036.125. As
explained at proposal, we may review a manufacturer's information
describing the parameters and documentation for demonstrating proper
maintenance before granting certification for an engine family.
    The maintenance instructions requirements we are finalizing for the
remainder of 40 CFR 1036.125(h) are covered in the serviceability
discussion in Section IV.B.3 and inducements discussion in Section IV.C
of this preamble. As noted in Section IV.B.3, our serviceability
provisions supplement the service information provisions specified in
40 CFR 86.010-38(j).\346\
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    \346\ We are not migrating the service information provisions
into 40 CFR part 1036 in this rule.
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vi. Performing Scheduled Maintenance on Test Engines
    We are finalizing our proposed update to 40 CFR 1065.410(c) to
clarify that inspections performed during testing include electronic
monitoring of engine parameters. While we intended the proposed update
to include prognostic systems, the proposed text referred only to
electronic tools, and we are revising from the proposed text in the
final provision to include ``or internal engine systems'' to clarify.
Manufacturers that include prognostic systems as part of their engine
packages to identify or predict malfunctioning components may use those
systems during durability testing and would describe any maintenance
performed as a result of those systems, consistent with 40 CFR
1065.410(d), in their application for certification. We note that, to
apply these electronic monitoring systems in testing, the inspection
tool (e.g., prognostic system) must be readable without specialized
equipment so it is available to all customers or accessible at
dealerships and other service outlets consistent with CAA sections
202(m) and 206.
3. Serviceability
    This Section IV.B.3 describes the provisions we are finalizing to
improve serviceability, reduce mal-maintenance, and ensure owners are
able to maintain emission control performance throughout the entire in-
use life of heavy-duty engines. See section IV.B.2 of this preamble for
a discussion of manufacturers' obligations to provide maintenance
instructions to operators. Also see the preamble of the proposed rule
for further discussion of why EPA proposed these serviceability and
maintenance information provisions.\347\ The final serviceability and
maintenance information provisions were informed by comments, and we
summarize key comments in this section.\348\ We provide complete
responses to the serviceability-related comments in section 5 of the
Response to Comments.
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    \347\ See section IV.B.3. of the proposed preamble (87 FR 17517,
March 28, 2022).
    \348\ While we requested comment on several potential approaches
to improve serviceability of electric vehicles in the proposal (87
FR 17517, March 28, 2022), EPA is not taking final action on any
requirements related to this request at this time; we may consider
the comments provided on improved serviceability of electric
vehicles in future rulemakings relevant to electric vehicles. See
section 5.3 of the Response to Comments document for details on
comments received.
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i. Background
    Without proper maintenance, the emission controls on heavy-duty
engines may not function as intended, which can result in increased
emissions. Mal-maintenance, which includes delayed or improper repairs
and delayed or unperformed maintenance, can be intentional (e.g.,
deferring repairs due to costs) or unintentional (e.g., not being able
to diagnose the actual problem and make the proper repair).
    In the NPRM, EPA discussed stakeholder concerns with the
reliability of MY 2010 and later heavy-duty engines, and significant
frustration expressed by owners concerning their experiences with
emission control systems on such engines. EPA explained that
stakeholders have communicated to EPA that, although significant
improvements have been made to emission control systems since they were
first introduced into the market, reliability and serviceability
continue to cause them concern. EPA received comments on the NPRM
further highlighting problems from fleets, owners, and operators.
Commenters noted issues with a range of emission-related components,
including: Sensors (DPF and SCR-related), DEF dosers, hoses, filters,
EGR valves, EGR coolers and EGR actuators, SCR catalysts, DOC, turbos,
wiring, decomposition tubes, cylinder heads, and DPFs. Specifically,
for example, comments included described experiences with
aftertreatment wiring harness failures, DEF nozzles plugging or over-
injecting, NOX sensor failures, defective DEF pumps and
level sensors, systems being less reliable in rain and cold weather,
more frequent required cleaning of DPFs than anticipated, and problems
related to DEF build-up. See section 5 of the Response to Comment for
further information and the detailed comments.
    In addition to existing labeling, diagnostic, and service
information requirements, EPA proposed to require important maintenance
information be made available in the owner's manual as a way to improve
factors that may contribute to mal-maintenance. The proposed
serviceability provisions were expected to result in better service
experiences for independent repair technicians, specialized repair
technicians, owners who repair their own equipment, and possibly
vehicle inspection and maintenance technicians. Furthermore, the
proposed provisions were intended to improve owner experiences
operating and maintaining heavy-duty engines and provide greater
assurance of long-term in-use emission reductions by reducing the
likelihood of occurrences of tampering.
    Given the importance and complexity of emission control systems and
the

impact to drivers for failing to maintain such systems (e.g.,
inducements), EPA believes it is critical to include additional
information about emission control systems in the owner's manual. We
proposed to require manufacturers to provide more information
concerning the emission control system in the owner's manual to include
descriptions of how the emissions systems operate, troubleshooting
information, and diagrams. EPA has imposed similar requirements in the
past, such as when EPA required vacuum hose diagrams be included on the
emission label to improve serviceability and help inspection and
maintenance facilities identify concerns with that system.\349\
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    \349\ See 53 FR 7675, March 9, 1988, and 55 FR 7177, February
29. 1990 for more information.
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ii. Final Maintenance Information Requirements for Improved
Serviceability
    EPA received both supportive and adverse comments from a number of
stakeholders on the serviceability proposals (see section 5 of the
Response to Comments). For example, comments from service providers and
manufacturers largely objected to the proposed serviceability
requirements, while owners and operators supported the proposed
requirements. EPA is finalizing requirements for improved
serviceability so that owners and operators can more easily understand
advanced emission control system operation and identify issues in such
systems as they arise during operation. To the extent EPA can ensure
this information is harmonized among manufacturers, we believe this
will improve the experiences of owners, operators, parts counter
specialists, and repair technicians, and reduce frustration that could
otherwise create an incentive to tamper.
    CAA section 207(c)(3)(A) requires manufacturers to provide
instructions for the proper maintenance and use of a vehicle or engine
by the ultimate purchaser and requires such instructions to correspond
to EPA regulations. The final rule includes maintenance provisions
migrated and updated from 40 CFR part 86, subpart A, to a new 40 CFR
1036.125, that specify the maintenance instructions manufacturers must
provide in an owner's manual to ensure that owners can properly
maintain their vehicles (see Section IV.B.2). Additionally, as a part
of the new 40 CFR 1036.125(h), we are finalizing specific maintenance
information manufacturers must provide in the owner's manual to improve
serviceability:
     EPA is finalizing with revision the proposed requirement
for manufacturers to provide a description of how the owner can use the
OBD system to troubleshoot problems and access emission-related
diagnostic information and codes stored in onboard monitoring systems.
The revision replaces the proposed requirement that the owner's manual
include general information on how to read and understand OBD codes
with a more specific set of required information. The final requirement
specifies that, at a minimum, manufacturers provide a description of
how to use the OBD system to troubleshoot and access information and
codes, including (1) identification of the OBD communication protocol
used, (2) location and type of OBD connector, (3) a brief description
of what OBD is (including type of information stored, what a
malfunction indicator light (MIL) is, explanation that some MILs may
self-extinguish), and (4) a note that certain engine and emission data
is publicly available using any scan tool, as required by EPA. As we
describe further in section IV.C.1.iii, we are not taking final action
on the proposed health monitors. Therefore, we are also not requiring
manufacturers to provide information about the role of the health
monitor to help owners service their engines before components fail in
the description of the OBD system.
     EPA is finalizing as proposed, with a few clarifications
in wording, a requirement for manufacturers to identify critical
emission systems and components, describe how they work, and provide a
general description of how the emission control systems operate.
     EPA is finalizing as proposed the requirement for
manufacturers to include one or more diagrams of the engine and its
emission-related components, with two exceptions: (1) We are not
finalizing the proposed requirements to include the identity, location,
and arrangement of wiring in the diagram, and we are not requiring
information related to the expected pressures at the particulate filter
and exhaust temperatures throughout the aftertreatment system. The
final requirement specifies the following information is required, as
proposed:
    [cir] The flow path for intake air and exhaust gas.
    [cir] The flow path of evaporative and refueling emissions for
spark-ignition engines, and DEF for compression-ignition engines, as
applicable.
    [cir] The flow path of engine coolant if it is part of the emission
control system described in the application for certification.
    [cir] The identity, location, and arrangement of relevant emission
sensors, DEF heater and other DEF delivery components, and other
critical emission-related components.
    [cir] Terminology to identify components must be consistent with
codes the manufacturer uses for the OBD system.
     EPA is revising the proposed requirement relating to
exploded-view drawings and basic assembly requirements in the owner's
manual. The final provision replaces a general reference to
aftertreatment devices with a specific list of components that should
be included in one or more diagrams in the owner's manual, including:
EGR Valve, EGR actuator, EGR cooler, all emission sensors (e.g.,
NOX, soot sensors, etc.), temperature and pressure sensors
(EGR, DPF, DOC, and SCR-related, including DEF-related temperature and
pressure sensors), fuel (DPF-related) and DEF dosing units and
components (e.g., pumps, filters, metering units, nozzles, valves,
injectors), DEF quality sensors, DPF filter, DOC, SCR catalyst,
aftertreatment-related control modules, any other DEF delivery-related
components (e.g., lines and freeze protection components), and
aftertreatment-related wiring harnesses if replaceable separately. The
revision also notes that the information could be provided in multiple
diagrams. We are also revising the proposed requirement to include part
numbers for all components in the drawings and instead are only
requiring part numbers for sensors and filters related to SCR or DPF
systems. We are not finalizing at this time the broader requirement
that this information include enough detail to allow a mechanic to
replace any of these components. Finally, once published for a given
model year, manufacturers will not be required to revise their owner's
manual with updated part numbers if a part is updated in that model
year. We recognize that manufacturers are able to use outdated part
numbers to find updated parts.
     EPA is finalizing as proposed the requirement for
manufacturers to provide a statement instructing owners or service
technicians where and how to find emission recall and technical repair
information available without charge from the National Highway Traffic
Safety Administration.\350\
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    \350\ NHTSA provides this information at https://www.nhtsa.gov/recalls. For example, manufacturers should specify if the
information would be listed under ``Vehicle'' or ``Equipment.''
---------------------------------------------------------------------------

     EPA is finalizing with some modifications from the
proposal the requirement for manufacturers to

include a troubleshooting guide to address SCR inducement-related and
DPF regeneration-related warning signals. For the SCR system this
requirement includes:
    [cir] The inducement derate schedule (including indication that DEF
quantity-related inducements will be triggered prior to the DEF tank
being completely empty).
    [cir] The meaning of any trouble lights that indicate specific
problems (e.g., DEF level).
    [cir] A description of the three types of SCR-related derates (DEF
quantity, DEF quality and tampering) and a notice that further
information on the cause of (e.g., trouble codes) is available using
the OBD system.
     For the DPF system the troubleshooting guide requirement
includes:
    [cir] Information on the occurrence of DPF-related derates.
    [cir] EPA is finalizing in 40 CFR 1036.110(c) that certain
information must be displayed on-demand for operators. Specifically,
EPA is finalizing the requirement that for SCR-related inducements,
information such as the derate and associated fault code must be
displayed on-demand for operators (see section IV.D.3 for further
information). EPA is also finalizing requirements that the number of
DPF regenerations, DEF consumption rate, and the type of derate (e.g.,
DPF- or SCR-related) and associated fault code for other types of
emission-related derates be displayed on-demand for operators (see
section IV.C.1.iii for further information).
    EPA proposed that manufacturers include a Quick Response (QR) code
on the emission label that would direct repair technicians, owners, and
inspection and maintenance facilities to a website providing critical
emission systems information at no cost. We are not taking final action
at this time on the proposed requirement to include QR codes on the
emission control information label. After considering manufacturers'
comments, we intend to engage in further outreach and analysis before
adopting electronic labeling requirements, such as QR codes. In this
rule, we are instead finalizing that the owner's manual must include a
URL directing owners to a web location for the manufacturer's service
information required in 40 CFR 86.010-38(j). We recognize the potential
for electronic labels with QR codes or similar technology to provide
useful information for operators, inspectors, and others. Manufacturers
from multiple industry sectors are actively pursuing alternative
electronic labeling. In the absence of new requirements for electronic
labeling, manufacturers must continue to meet requirements for applying
physical labels to their engines. Manufacturers may include on the
vehicle or engine any QR codes or other electronic labeling information
that goes beyond what is required for the physical emission control
information label. EPA is also not taking final action at this time on
the proposed requirement to include a basic wiring diagram for
aftertreatment-related components in the owner's manual. Finally, EPA
is not taking final action at this time on requirements related to DPF
cleaning; instead, EPA intends to continue to follow the work CARB has
undertaken in this area and may consider taking action in a future
rule.
iii. Other Emission Controls Education Options
    In addition to our proposed provisions to provide more easily
accessible service information for operators, we sought comment on
whether educational programs and voluntary incentives could lead to
better maintenance and real-world emission benefits. We received
comments in response to the NPRM supportive of improving such
educational opportunities to promote an understanding of how advanced
emission control technologies function and the importance of emissions
controls as they relate to the broader economy and the environment (see
section 5.4 of the Response to Comment for further details). EPA is not
finalizing any requirements related to this request for comment at this
time but will look for future opportunities to improve the availability
of information on emission control systems.

C. Onboard Diagnostics

    As used here, the terms ``onboard diagnostics'' and ``OBD'' refer
to systems of electronic controllers and sensors required by regulation
to detect malfunctions of engines and emission controls. EPA's OBD
regulations for heavy-duty engines are contained in 40 CFR 86.010-18,
which were initially promulgated on February 24, 2009 (74 FR 8310).
Those requirements were harmonized with CARB's OBD program then in
place. Consistent with our authority under CAA section 202(m), EPA is
finalizing an update to our OBD regulations in 40 CFR 1036.110 to align
with existing CARB OBD requirements as appropriate, better address
newer diagnostic methods and available technologies, and to streamline
provisions.
1. Incorporation of California OBD Regulations by Reference
    CARB OBD regulations for heavy-duty engines are codified in title
13, California Code of Regulations, sections 1968.2, 1968.5, 1971.1,
and 1971.5. EPA is finalizing our proposal to incorporate by reference
in 40 CFR 1036.810 the OBD requirements CARB adopted October 3,
2019.351 352 In response to the NPRM, EPA received a number
of comments supportive of EPA's adoption of the revised CARB OBD
program, including the 2019 rule amendments. As discussed in this
section and reflected in final 40 CFR 1036.110(b), our final rule will
harmonize with the majority of CARB's existing OBD regulations, as
appropriate and consistent with the CAA, and make these final
requirements mandatory beginning in MY 2027 and optional in earlier
model years. These new requirements better address newer diagnostic
methods and available technologies and have the additional benefit of
being familiar to industry. For example, the new tracking requirements
contained in CARB's updated OBD program, known as the Real Emissions
Assessment Logging (``REAL'') program, track real-world emissions
systems performance of heavy-duty engines. The REAL tracking
requirements include the collection of onboard data using existing OBD
sensors and other vehicle performance parameters, which will better
allow the assessment of real world, in-use emission performance.
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    \351\ This CARB rulemaking became effective the same day and
began to phase in under CARB's regulations with MY 2022. The CARB
regulations we are adopting are available at: https://ww2.arb.ca.gov/resources/documents/heavy-duty-obd-regulations-and-rulemaking.
    \352\ The legal effect of incorporation by reference is that the
material is treated as if it were published in the Federal Register
and CFR. This material, like any other properly issued rule, has the
force and effect of law. Congress authorized incorporation by
reference in the Freedom of Information Act to reduce the volume of
material published in the Federal Register and CFR. (See 5 U.S.C.
552(a) and 1 CFR part 51). See https://www.archives.gov/federal-register/cfr/ibr-locations.html for additional information.
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    EPA's final OBD requirements are closely aligned with CARB's
existing requirements with a few exceptions, as further described in
Section IV.C.1.i. We are finalizing exclusions to certain provisions
that are not appropriate for a Federal program and including additional
elements to improve on the usefulness of OBD systems for operators.

i. CARB OBD Provisions Revised or Not Included in the Finalized Federal
Program
    CARB's 2019 OBD program includes some provisions that may not be
appropriate for the Federal regulations.\353\ In a new 40 CFR
1036.110(b), we are finalizing the following clarifications and changes
to the 2019 CARB regulations that we are otherwise incorporating by
reference:
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    \353\ EPA is reviewing a waiver request under CAA section 209(b)
from California for the Omnibus rule; note, we are making no
determination in this action about the appropriateness of these
provisions for CARB's regulation.
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    1. Modifying the threshold requirements contained in the 2019 CARB
OBD standards we are adopting (as discussed in Section IV.C.1.ii),
    2. Providing flexibilities to delay compliance up to three model
years for small manufacturers who have not previously certified an
engine in California,
    3. Allowing good engineering judgment to correlate the CARB OBD
standards with EPA OBD standards,
    4. Clarifying that engines must comply with OBD requirements
throughout EPA's useful life as specified in 40 CFR 1036.104, which may
differ from CARB's required useful life for some model years,
    5. Clarifying that the purpose and applicability statements in 13
CCR 1971.1(a) and (b) do not apply,
    6. Not requiring the manufacturer self-testing and reporting
requirements in 13 CCR 1971.1(l)(4) ``Verification of In-Use
Compliance'' and 1971.5(c) ``Manufacturer Self-Testing'' (note, in the
proposal we inadvertently cited incorrect CARB provisions for the
intended referenced requirements),
    7. Retaining our existing deficiency policy (which we are also
migrating into 40 CFR 1036.110(d)), adjusting our deficiency timing
language to match CARB's, and specifying that the deficiency provisions
in 13 CCR 1971.1(k) do not apply,
    8. Requiring additional freeze frame data requirements (as further
explained in Section IV.C.1.iii),
    9. Requiring additional data stream parameters for compression- and
spark-ignition engines (as further explained in Section IV.C.1.iii),
and
    10. Providing flexibilities to reduce redundant demonstration
testing requirements for engines certified to CARB OBD requirements.
    With regard to the second through the fifth items, EPA is
finalizing these requirements as proposed for the reasons stated in the
proposal. For the sixth item, EPA is finalizing this requirement for
the reasons stated in the proposal and as proposed with the exception
of a correction to the CARB reference we cited.
    EPA received supportive comment from manufacturers on our proposal
to migrate our existing deficiency requirements, and adverse comment
from manufacturers and CARB requesting that EPA harmonize with CARB's
retroactive deficiency provisions. CARB's deficiency requirements are
described in 13 CCR 1971.1(k) and include descriptions of requirements
such as how deficiencies are granted, fines charged for deficiencies,
allowable timelines, and the application of retroactive deficiencies.
We are finalizing as proposed to migrate our existing approach to
deficiency provisions in 40 CFR 86.010-18(n) into 40 CFR
1036.110(d).\354\ See section 7.1 of the Response to Comments for
further details on comments received and EPA's responses.
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    \354\ See 74 FR 8310, 8349 (February 24, 2009).
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    EPA also received comment concerned with EPA's regulatory language
describing the allowable timeframe for deficiencies. Commenters said
EPA's proposed deficiency timeline is shorter than CARB's and that EPA
should harmonize with CARB and provide manufacturers with 3 years to
make hardware-related changes. EPA is finalizing a change to 40 CFR
1036.110(d)(3) to ensure our language is consistent with CARB's
deficiency timeline in 13 CCR 1971.1(k)(4).
    EPA received supportive and adverse comment on the proposal to
require additional freeze frame data requirements, including that the
reference in our regulations was overly broad and possibly in error.
EPA is finalizing these requirements with revisions to those proposed
in 40 CFR 1036.110(b)(8) to be more targeted. It is critical for there
to be sufficient emissions-related parameters captured in freeze frame
data to enable proper repairs.
    EPA received supportive and adverse comment on the proposal to
require additional data stream parameter requirements, including
comment that our regulations needed to be more specific. EPA is
finalizing these requirements with revisions to those proposed in 40
CFR 1036.110(b)(9) to properly capture the additional elements we
intended to add to the freeze frame and to ensure these additional
parameters are interpreted properly as an expansion of the existing
data stream requirements in 13 CCR 1971.1(h)(4.2). Access to important
emissions-related data parameters is critical for prompt and proper
repairs.
    EPA is finalizing flexibilities to reduce redundant demonstration
testing requirements for engines certified to CARB OBD requirements,
see section IV.C.1.iv. of this preamble for further discussion on what
we are finalizing.
    It is important to emphasize that by not incorporating certain
existing CARB OBD requirements (e.g., the ``Manufacturer Self-Testing''
requirements) into our regulations, we are not waiving our authority to
require such testing on a case-by-case basis. CAA section 208 gives EPA
broad authority to require manufacturers to perform testing not
specified in the regulations in such circumstances. Thus, should we
determine in the future that such testing is needed, we would retain
the authority to require it pursuant to CAA section 208.
ii. OBD Threshold Requirements
a. Malfunction Criteria Thresholds
    Existing OBD requirements specify how OBD systems must monitor
certain components and indicate a malfunction prior to when emissions
would exceed emission standards by a certain amount, known as an
emission threshold. Emission thresholds for these components under the
existing requirements in the 2019 CARB OBD update that we are
incorporating by reference are generally either an additive or
multiplicative value above the applicable exhaust emission standard.
EPA proposed to modify the threshold requirements in the 2019 CARB OBD
update to be consistent with the provisions finalized by CARB in their
Omnibus rule in December of 2021 and not tighten threshold requirements
while finalizing lower emission standards.\355\ \356\ This meant, for
example, that for monitors required to detect a malfunction before
NOX emissions exceed 1.75 times the applicable existing
NOX standard, the manufacturer would continue to use the
same numeric threshold (e.g., 0.35 g/bhp-hr NOX) for the new
emission standards finalized in this rule.
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    \355\ California Air Resources Board. Staff Report: Addendum to
the Final Statement of Reasons for Rulemaking--Public Hearing to
Consider the Proposed Heavy-Duty Engine and Vehicle Omnibus
Regulation and Associated Amendments. December 20, 2021. https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2020/hdomnibuslownox/fsoraddendum.pdf.
    \356\ EPA is reviewing a waiver request under CAA section 209(b)
from California for the Omnibus rule; note, we are making no
determination in this action about the appropriateness of these
provisions for CARB's regulation.
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    EPA received comments from manufacturers and operators in support

of finalizing the threshold provisions as proposed, and a comment from
CARB stating that three engine families have recently been certified to
lower FELs indicating EPA should finalize lower thresholds. We note
that CARB stated that two of these engine families were certified with
deficiencies, and thus these engines did not fully meet all specific
OBD requirements (see section 7.1 of the Response to Comment for
further detail about these comments and EPA's responses). EPA is
finalizing with minor revision future numerical values for OBD
NOX and PM thresholds that align with the numerical value
that results under today's NOX and PM emissions
requirements.
    We are finalizing as proposed a NOX threshold of 0.40 g/
hp-hr and a PM threshold of 0.03 g/hp-hr for compression-ignition
engines for operation on the FTP and SET duty cycles. We are finalizing
as proposed a PM threshold of 0.015 g/hp-hr for spark-ignition engines
for operation on the FTP and SET duty cycles. For spark-ignition
engines, we proposed NOX thresholds of 0.30 and 0.35 g/hp-hr
for monitors detecting a malfunction before NOX emissions
exceed 1.5 and 1.75 times the applicable standard, respectively. We are
finalizing these numeric threshold values without reference to what
percent exceedance is relevant and instead are clarifying that the
0.35g/hp-hr standard applies for catalyst monitors and that 0.30g/hp-hr
applies for all other monitors, to ensure the proper numeric thresholds
can be applied to engines certified under 13 CCR 1968.2 and 1971.1..
EPA intends to continue to evaluate the capability of HD OBD monitors
to accommodate lower thresholds to correspond to the lower emission
levels for the final emission standards and may consider updating
threshold requirements in the future as more in-use data becomes
available.
    We also inadvertently omitted from the proposed 40 CFR 1036.110(b)
the specific threshold criteria for SI and CI engine HC and CO
emissions that coincided with our overall expressed intent to harmonize
with the threshold requirements included in CARB's Omnibus rule and not
tighten OBD emission thresholds.\357\ Consistent with this intent, we
are finalizing a provision in 40 CFR 1036.110(b)(5) that instructs
manufacturers to use numeric values that correspond to existing HC and
CO standards (0.14 g/hp-hr for HC, 15.5 g/hp-hr for CO from
compression-ignition engines, and 14.4 g/hp/hr for spark-ignition
engines) to determine the required thresholds. Applying this
methodology will result in calculations that produce thresholds
equivalent to existing thresholds. Including this clarification avoids
unintentionally lowering such thresholds.
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    \357\ While CARB standards refer to nonmethane hydrocarbon
standards as ``NMHC'' EPA's regulation refers to ``HC'' generically
for such standards, but we define HC in 40 CFR 1036.104 to be NMHC
for gasoline- and diesel-fueled engines.
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b. Test-Out Criteria
    CARB OBD requirements include ``test-out'' provisions in 13 CCR
1968.2 and 1971.1 which allow manufacturers to be exempt from
monitoring certain components if failure of these components meets
specified criteria.\358\ EPA is adopting these test-out provisions
through the incorporation by reference of CARB's updated 2019 OBD
requirements. Similar to the revisions we proposed and are finalizing
for malfunction criteria, EPA's assessment is that for compression
ignition engines test-out criteria should also not be tightened at this
time. However, we inadvertently omitted from the proposed 40 CFR
1036.110(b) the specific adjustments to test-out criteria for
compression-ignition engines included in CARB's Omnibus rule that are
necessary to result in such criteria not being tightened. Consistent
with our overall expressed intent to (1) not tighten OBD requirements,
and (2) modify the 2019 CARB requirements we are adopting by
harmonizing with the numeric values included in CARB's Omnibus rule, we
are finalizing a revision from the proposal to include test-out
criteria calculation instructions into our regulations.
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    \358\ ``Test-out'' provisions may be identified in CARB OBD
regulations specifically as ``test-out'' requirements or through
language describing that certain components or systems are ``exempt
from monitoring'' if manufacturers can demonstrate certain
conditions are met.
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    Specifically, we are finalizing a provision that manufacturers
seeking to use the test-out criteria to exempt engines from certain
monitoring in the incorporated by reference 2019 CARB regulations 13
CCR 1968.2 and 1971.1 must calculate the criteria based on specified
values provided in 40 CFR 1036.110(b)(5). For example, 13 CCR
1971.1(e)(3.2.6) specifies that one of the requirements for an EGR
catalyst to be exempt from monitoring is if no malfunction of the EGR
catalyst can cause emissions to increase by 15 percent or more of the
applicable standard as measured from the appropriate test cycle. The
requirement we are finalizing in 40 CFR 1036.110(b)(5) instructs
manufacturers to use specific values for that ``applicable standard''
to calculate the required test-out criteria. For example, for the EGR
catalyst test-out provision, this would result in a NOX
test-out criterion of 0.03 g/hp-hr (0.2 g/hp-hr  0.15).
Including this provision is consistent with the intent of our proposal
and avoids unintentionally lowering such test-out criteria that would
render such test-out criteria generally inconsistent with the other
provisions we are finalizing in 40 CFR 1036.110(b)(5), and enables
manufacturers to continue using these provisions.
c. Applicable Thresholds for Engines Certified to 40 CFR Part 1036 Used
in Heavy-Duty Vehicles Less Than 14,000 Pounds GVWR
    We are finalizing as proposed that engines installed in vehicles at
or below 14,000 lbs GVWR are subject to OBD requirements under the
light-duty program in 40 CFR 86.1806-17. Commenters pointed out that
the proposed rule did not specify alternative thresholds for engines
certified to 40 CFR part 1036 on an engine dynamometer that are subject
to OBD requirements under 40 CFR 86.1806-17. Without such a provision,
manufacturers would be subject to the existing thresholds in 40 CFR
86.1806-17 that are based on standards set for light-duty chassis-
certified vehicles. Consistent with our statements in the NPRM that our
proposal intended to harmonize with the threshold requirements included
in CARB's Omnibus policy and not lower emission threshold levels in our
proposed OBD regulations, we are clarifying in 40 CFR 86.1806-17(b)(9)
that the thresholds we are finalizing in 40 CFR 1036.110(b)(5) apply
equally for engines certified under 40 CFR part 1036 that are used in
vehicles at or below 14,000 lbs GVWR.
iii. Additional OBD Provisions in the Proposed Federal Program
    In the NPRM, EPA proposed to include additional requirements to
ensure that OBD can be used to properly diagnose and maintain emission
control systems to avoid increased real-world emissions. This was also
a part of our effort to update EPA's OBD program and respond to
numerous concerns raised in the ANPR about the difficulty of diagnosing
and maintaining proper functionality of advanced emission control
technologies and the important role accessible and robust diagnostics
play in this process. At this time, after consideration of comments, we
are finalizing a limited set of these proposed provisions (see section
7 of the Response to Comments documents for further detail on comments
and

EPA's responses). Where OBD requirements between EPA and CARB may
differ, EPA is finalizing as proposed provisions allowing us to accept
CARB OBD approval as long as a manufacturer can demonstrate that the
CARB program meets the intent of EPA OBD requirements and submits
documentation as specified in 40 CFR 1036.110(b).
    In this section we describe the final additional EPA certification
requirements in 40 CFR 1036.110 for OBD systems, which, consistent with
CAA section 202(m),\359\ are intended to provide more information and
value to the operator and play an important role in ensuring expected
in-use emission reductions are achieved long-term. With respect to our
proposed provisions to require additional information from OBD systems
be made publicly available, we received supportive comments from
operators and adverse comments from manufacturers. After considering
these comments, we are revising our final provision from those
proposed, as summarized here and provide in more detail in section 7 of
the Response to Comments document. We are not taking final action at
this time on the proposed requirement to include health monitors. In
addition to driver information requirements we are adopting to increase
the availability of serviceability and inducement-related information
(see section IV.B.3 and IV.D.3 respectively of this preamble), we are
also finalizing in 40 CFR 1036.110(c) that the following information
must be made available in the cab on-demand in lieu of the proposed
health monitors:
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    \359\ For example, CAA section 202(m)(5) specifies that by
regulation EPA shall require (subject to an exception where
information is entitled to protection as trade secrets)
manufacturers to provide promptly to any person engaged in the
repairing or servicing of heavy-duty engines with any and all
information needed to make use of the emission control diagnostics
system required under CAA section 202 and such other information
including instructions for making emission related diagnosis and
repairs.
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     The total number of diesel particulate filter regeneration
events that have taken place since installing the current particulate
filter.
     Historical and current rate of DEF consumption (e.g.,
gallons of DEF consumed per mile or gallons of DEF consumed per gallon
of diesel fuel consumed.) This information is designed such that
operators can reset it as needed to capture specific data for
comparison purposes.
     For AECD conditions (outside of inducements) related to
SCR or DPF systems that derate the engine (e.g., either a speed or
torque reduction), the fault code for the detected problem, a
description of the fault code, and the current restriction.
    For all other health monitor provisions proposed in 40 CFR
1036.110(c)(3), we are not taking final action on those proposed
provisions at this time.
    In addition to incorporating an improved list of publicly available
data parameters by harmonizing with updated CARB OBD requirements, in
40 CFR 1036.110(b)(9) EPA is finalizing as proposed for the reasons
explained further in the proposal to add signals to the list, including
to specifically require that all parameters related to fault conditions
that trigger vehicle inducement also be made readily available using
generic scan tools. EPA expects that each of these additional
requirements will be addressed even where manufacturers relied in part
on a CARB OBD approval to satisfy Federal requirements in order to
demonstrate under 40 CFR 1036.110(b) that the engine meets the intent
of 40 CFR 1036.110. The purpose of including additional parameters is
to make it easier to identify malfunctions of critical aftertreatment
related components, especially where failure of such components would
trigger an inducement. We are revising the proposed new parameters for
HD SI engines in 40 CFR 1036.110(b)(10) after considering comments. See
section 3 of the Response to Comments.
    We are also finalizing a general requirement in 40 CFR
1036.110(b)(9)(vi) to make all parameters available that are used as
the basis for the decision to put a vehicle into an SCR- or DPF-related
derate. For example, if the failure of an open-circuit check for a DEF
quality sensor leads to an engine inducement, the owner/operator would
be able to identify this fault condition using a generic scan tool. We
are finalizing a requirement that manufacturers make additional
parameters available for all engines so equipped,\360\ including:
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    \360\ Memorandum to Docket EPA-HQ-OAR-2019-0055: ``Example
Additional OBD Parameters''. Neil Miller, Amy Kopin. November 21,
2022.
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      For Compression Ignition engines:

[cir] Inlet DOC and Outlet DOC pressure and temperature
[cir] DPF Filter Soot Load (for all installed DPFs)
[cir] DPF Filter Ash Load (for all installed DPFs)
[cir] Engine Exhaust Gas Recirculation Differential Pressure
[cir] DEF quality-related signals
[cir] Parking Brake, Neutral Switch, Brake Switch, and Clutch Switch
Status
[cir] Aftertreatment Dosing Quantity Commanded and Actual
[cir] Wastegate Control Solenoid Output
[cir] Wastegate Position Commanded and Actual
[cir] DEF Tank Temperature
[cir] DEF Doser Control Status
[cir] DEF System Pressure
[cir] DEF Pump Commanded Percentage
[cir] DEF Coolant Control Valve Control Position Commanded and Actual