Past trouble

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Refer to "How to treat past trouble" ( HOW TO TREAT PAST TROUBLE ) for proceeding the diagnostics. Diagnose mainly wiring harness or connector failure in the CAN bus lines between the engine control module and AWD-ECU, and malfunction in the power supply system for the engine control module.
NOTE: For a past trouble, you cannot find it by the scan tool MB991958 CAN bus diagnostics even if there is any failure in CAN bus lines. In this case, check the CAN bus lines in the same manner as How to cope with intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ). You can narrow down the possible cause of the trouble by referring to the DTC, which is set regarding the CAN communication-linked ECUs. (Refer to CAN BUS LINE DIAGNOSTIC FLOW .)