Circuit Description

This DTC indicates that a transmission related OBD-II failure has occurred. Transmission Control Module (TCM) controls a dedicated service transmission light, which is illuminated when a failure is reported by certain non-emission related TCM diagnostics. TCM has no direct control of engine MIL, but if transmission fault occurs that is emission related, MIL must illuminate. A MIL request circuit between ECM and TCM provides a means for illuminating MIL, even though fault was detected by TCM. This circuit is increased to battery voltage within ECM. To illuminate MIL, TCM lowers circuit voltage. ECM detects this and DTC is set, which illuminates MIL.

Conditions required to set DTC are:

• A short to ground, open or short to voltage detected on MIL request circuit.
• Condition is present for at least 2.5 seconds.