As all modern cars to engine diagnostics you need a computer. Best of all is Renault VDIAG or CAN-CLIP but it can be ddt2000 or other diagnostics devieces. In Laguna IDE (CAN) is the ability to read the all parameters and faults DF and and the circumstances DEF. In the Megane IDE diagnostics is limited and there are no circumstances.

     Most universal diagnostic software connects to the engine computer F5R (Sirius 3H, Sirius 35), but often read faults or parameter does not match the reality, and even can be confusing so it is best to use Clip.
     Although this part of the damage can be localized on the basis of symptoms and simple voltmeter.


When the
lights up and stop the engine temperature and the engine turns off after 5 seconds is the most common cause is damage to the fuel regulator. The phenomenon begins to occur mostly in hot engine when stationary in traffic. With time, it begins to increase, practically impossible ride. The temperature controller then exceeds 80 ° C. This can be a temporary remedy, including air conditioning. Then turn on the fan and slightly lowers the temperature controller. This is a situation when a computer tries to open the control valve to reduce the pressure, but the valve can not be opened and the pressure does not drop. The computer treats it as a loss of control over pressure in the terminal for security and emergency engine off by turning off the electric pump pre. In this case, the controller is suitable for regeneration.

     It should be noted that the computer can also turn off the engine in case of excessive heat, damage, pressure sensor and EGR valve failure (Megane)
     Below are charts of the pressure control in Laguna II IDE.


Limp mode when the injection system at idle or during an acute acceleration above 3000 rpm cause is insufficient pressure in the injection rail. The reasons may be several:

  •     low initial performance electric fuel pump. You can check it by measuring pressure (4.5-5 bar). In the absence of gauge can measure the approximate performance by disconnecting the fuel line and admitting him to a separate tank. Then we close the fuel pump relay for 1 min. The pump should fill at least 2.75 liters of gasoline.
  •     clogged fuel filter. The filter should be replaced every 60 thousand km. It is located under the floor in the vicinity of the fuel tank or the fuel tank inside the pump unit (Laguna II).
  •     wear or damage to the high pressure pump. Pump operates somewhat "dry" because gasoline does not have lubricating properties. In addition, impurities in the fuel (mainly sulfur compounds) cause precipitation of sludge that turn into sandpaper and destroy the pump seal. Efficiency is best to check with your diagnosis after eliminating the first two points. The pressure should be in the range 60-100 bar. Pressure also can be made using a simple voltmeter. Connect it to the wires 2 and 3 of the pressure sensor. About 0.5 V voltage should be present with the ignition on. After starting the engine voltage increases with pressure. It should range between 2.2 V and 3 V with 2.2 V corresponds to the pressure of 60bar and 90bar 3V. When the voltage rises above 3.2 V 125bar pressure is exceeded and there is an emergency engine shutdown. Fuel pump is also visible on the black sediment in the filter located at the entrance to the injection moldings.
  •     A leak in the high pressure system. Carefully check your pump seal, a raild, a pressure sensor and a pressure regulator. Often the cause of leakage is the lower o-ring of regulator which separates the high-pressure part of the low pressure. Often the cause is damage to the surface of the rail at the lower o-ring that is formed by removing the regulator mismanagement. The original rubber o-ring in the size 7x1, 5 best replace fluoride in the size of 7.1 x 1, 6 O-rings are more resistant fluorine mechanically, chemically, and can withstand temperatures up to 200 ° C.
  •     faulty pressure regulator. Leakage of needle valve ball in the regulator is driven consumption (over the course of 200.000 miles) or the more pollution that could fall into an open fuel system. Therefore, attention should be paid to the cleanliness of the dismantling of the fuel system. If the valve is not clear that the problem of valve leakage generally disqualifies it completely, although in some cases, the exchange of the same ball valve seal recovers. If the socket is damaged problem is greater because due to the thin wall is generally not possible sanding zaworku ball and socket must be brought new.


Malfunction indicator lamp. Determination of the cause illumination of the light requires a computer connection and read diagnostic errors. Mostly due to an open or short circuit in electrical circuits engine computer

Uneven idling

Uneven work especially at idle is a very common ailment engines going.
The causes can be divided into three groups: the ignition system , fuel injection system and the engine itself . But before we do anything that you connect the Clip and check that the computer does not see any error , in particular camshaft sensor and flywheel .

  • First we need to check that is the leading cause of ignition . Top replace a coil of wire and put new spark . Damage to the coil until it breaks you can not see , like the leads if upali the cable when connected to a terminal , the spark is formed inside the pipe from the outside you can not see .
  • If the ignition system is efficient check the pressure in the cylinders. Nominally, it should be above 14 bar , it is possible tolerance to 10% between the highest and lowest score . In the case of a reduction of compression is most responsible for leaking valves.
  • If the compression pressure is correct , the next step is to check the injector , the damage is rare but it does happen and you need to take the pressure reading at idle. This happens for example when the clogged filter pressure regulator or damage to the regulator , the pressure can surge and a very wide range (below is the course of the Megane 29-100 bar) and the steepest decline can fall ignitions .
  • If you are still not solved the problem, check the belt. Very often there is an incorrect setting of the pulley shaft exhaust valves . Delay injection can reduce the flexibility of the engine and uneven work .
  • If the problem persists you should also check on the status of inlet . The engine is quite often the case early intake valve seals wear which leads sizing valves. The degree of sizing is uneven and where the greatest evil can cause the mixture in the cylinder.

Difficult to run the engine

    Direct injection engines should light in time to 2 seconds even in the most frosts. The main problem here is the time to reach the proper pressure injection system. During start-up regulator is virtually closed and high pressure pump with every turn causes an increase in pressure in the system. When it reaches the required 70-100 bar, the fuel is sprayed enough and the engine starts immediately.
    Time to reach the required pressure depends mainly on the performance of the high pressure pump, pressure regulator and the tightness of the system. By an efficient system time is less than 2 seconds. The rate of pressure rise in the system can be measured, including registration of pressure before starting the engine.
Main screen Clip interface 

Laguna 2.0 IdE (can) regulator fail

Laguna 2.0 IdE (can) regulator OK

leaking pressure regulator (damage slot or O-ring)
After about 15 seconds of idling turn on limp mode.
Shows the increase in the closure of the regulator to maintain set pressure.
After crossing the RCO value of 54% turn on limp mode.

Start-up fully functional engine

RCO value remaining at the level of over 30% after the engine has warmed up idling to poor performance
of high pressure pump. The value of the RCO under constant load should be between 25-35% .