Mechanic Certification in Engine Repair

by Fred Decker

Although computers and electronic devices get more of the limelight, diesel and gasoline engines are crucial to a modern economy. The cars and trucks that move citizens and goods around the country need regular maintenance, and so do lawnmowers, generators and motorcycles. The National Institute for Automotive Service Excellence offers a number of certifications for car, bus and truck technicians, and small-engine mechanics can earn certification from individual manufacturers.

Car and Light Truck Engines

The ASE offers a full series of certification exams for mechanics working with cars and light trucks, including two on engine repair. Test A1 covers gasoline engine repair, test A8 covers engine performance and test A9 assesses the mechanic's knowledge of light diesel engines. Each of these exams consists of 50 multiple-choice questions, some of which are not scored. Candidates for certification must have at least two years' practical experience in automotive repair. Two years of formal training at a technical or community college can be substituted for one year of work experience. Tests A1 and A8 are required for mechanics who want to achieve Master Automobile Technician status, but A9 is not.

Diesel Engine Certifications

For mechanics working with heavier vehicles, the ASE offers several additional engine-repair certifications. The T-series of truck certification tests includes T1, consisting of 50 multiple-choice questions on large gasoline engines, and T2, which has 55 multiple-choice questions on heavy diesels. T2 is required for Master Service Technician status, though T1 is not. The H-series exams for transit buses include H1, for compressed natural gas engines, and H2, for diesel engines. Both include 50 questions, and one or the other is needed for Master status. The S-series exams for school bus mechanics includes test S2, consisting of 55 questions on diesel engines. It's necessary for Master status.

Advanced Certifications

The ASE offers two advanced exams in engine performance for technicians at higher skill levels. The L1 test is oriented around automobiles, SUVs and light trucks, and it deals with the complexities of fuel and air induction, emission controls and other factors that can limit a vehicle's performance. Applicants must already hold the A8 certification and have two years' related experience. The L2 exam is a similarly detailed test on diesel engine performance, including fuel systems, electronic engine controls and exhaust systems. Candidates must already hold one of the standard diesel engine certifications, and have two years' experience.

Maintenance of Certification

All ASE certifications, including the advanced L1 and L2 certifications, are time-limited. Mechanics must take a recertification exam every five years to maintain their status. Master Service Technicians in any field must maintain each individual certification to keep their Master status.

Small Engine Repair

The lightweight engines used in lawnmowers, ATVs, rototillers, snowmobiles, generators and other power equipment don't have an equivalent to ASE certification. Technicians can learn their skills hands-on or through certificate programs at a vocational or technical school. The value of those certificates rests entirely on the school's local reputation. Large small-engine manufacturers, such as Rotax, Briggs & Stratton or Honda, offer factor certification to technicians at their own dealerships and service centers, which provides a more universal measure of competence.


The U.S. Bureau of Labor Statistics has projected steady if unspectacular job growth for mechanics in most disciplines. Diesel mechanics should see 15 percent job growth between 2010 and 2020, about the same as the average for all occupations. Demand for auto mechanics should grow by 17 percent over the same decade, and small engine mechanics will experience 21 percent job growth. Diesel mechanics have the highest median incomes of the three, at $40,850 per year. Auto mechanics enjoy a median income of $35,790, while small-engine mechanics earned a median income of $31,790.

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