Leon Mk2
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General to self-diagnosis
Features of self-diagnosis
The engine control unit (Motronic control unit J220) is equipped with a fault memory. If faults occur in the sensors and components being monitored, they will be stored in the fault memory together with an indication of the type of fault. After evaluating the information, the engine control unit decides among different faults => Fault table page 01-44 and stores these until the contents of the fault memory is erased. Faults which only occur sporadically will have the addendum "sporadic fault" on the print out. These faults will be indicated on the display by the addendum "/SP". The cause of sporadic faults can be e.g. a loose contact or a brief open circuit. If a sporadic fault does not occur again within 40 warm-up phases (engine start below 50° C coolant temperature - switched off above 72° C), it will be erased from the fault memory. The stored faults can be read out with the tester VAS 5051 . The fault memory must be erased after the faults have been eliminated => Page 01-18. If the fault memory has been erased, the engine control unit looses all the learnt values for Lambda, idling speed and charge pressure. Therefore substantial problems in driving characteristics may occur depending on vehicle mileage. If the engine control unit connectors are pulled off or the battery is disconnected, the learnt values for Lambda, idling speed and charge pressure will likewise be lost. However, the contents of the fault memory and the basic settings (EPC and exhaust gas recirculation) are retained. When the engine is subsequently started, the engine might idle roughly for a brief period. In this case, leave the engine running for a few minutes at idling speed or perform a longer test drive until the learning process is completed. Note: General information for self-diagnosis can be found in the instruction manuals for the fault reader V.A.G 1551, vehicle system tester V.A.G 1552 or the new tester VAS 5051. |
