On Board Diagnostics II (OBD II)

On Board Diagnostics system II (OBD II) is a statutory requirement.

When emission related malfunctions occur, the Transmission Control Module (TCM) can also activate the Malfunction Indicator Lamp (MIL) in the combined instrument panel. The MIL is controlled by the Engine Control Module (ECM). A transmission malfunction that affects exhaust emissions will cause a Diagnostic Trouble Code (DTC) to be posted and the TCM sends a request to the ECM to activate the MIL. The request to activate the MIL is maintained while the DTC, whether the fault is permanent or intermittent. This situation applies to the certain DTCs. On Board Diagnostic II (OBD II)

ECM Motronic 4.4 posts a DTC when the transmission sends a request for the MIL.