Circuit Description

This DTC indicates that a transmission-related OBD II failure has occurred. The Transmission Control Module (TCM) controls a dedicated Service Transmission Light (STL) which illuminates when a fault is reported by certain non-emissions-related TCM diagnostics. TCM has no direct control of engine MIL, but if transmission fault occurs that is emissions related, engine MIL must illuminate.

A MIL request circuit between the ECM and TCM provides a means for illuminating MIL, even though fault was detected by TCM. This circuit is pulled up to battery positive within the ECM. In order to illuminate the MIL, TCM pulls the circuit low. ECM detects this and sets DTC.

For this DTC to set, engine has to be cranking and MIL request circuit has to be shorted to ground, open, or shorted to battery voltage.