On-Board Diagnostics II (OBD II)

In some markets where an on-board diagnostics system II (OBD II) is a statutory requirement the transmission control module (TCM) can also activate the Malfunction Indicator Lamp (MIL) in the combined instrument panel. The malfunction indicator lamp is controlled by the engine control module (ECM).

If there is an exhaust emission-related transmission malfunction a diagnostic trouble code (DTC) will be stored and the transmission control module sends a request to the engine control module to activate the malfunction indicator lamp. The request to activate the malfunction indicator lamp is maintained while the diagnostic trouble code is stored, whether the fault is permanent or intermittent. This situation applies to the certain transmission diagnostic trouble codes.

The Motronic 4.4 engine control module posts a diagnostic trouble code when the transmission sends a malfunction indicator lamp request.