For 1990-2009 cars

When the rear defog input circuit 292 to the body control module (BCM) is momentarily switched to ground, as when the rear defog switch is pressed, the BCM will respond by grounding circuit 193, the coil of the rear defog relay.

This action energizes the rear defog relay providing power to circuit 293-rear defog heater elements. Circuit 193 also provides ground through the BCM for the rear defog ON/OFF indicator. The first time in an ignition cycle the rear defog is activated, the rear defog will remain ON for 15 minutes or until the ignition switch is turned OFF. If the rear defog is activated again during the same ignition cycle, the rear defog will remain ON for 7 1/2 minutes or until the ignition switch is turned Off. Pressing the rear defog button before the timer has expired will turn the rear defog function OFF.

#### DTC Parameters

• | The Ignition is in RUN

• | Circuit 193 is shorted-to-ground

| or

• | Rear defog is requested and circuit 193 is open

#### Diagnostic Aids:

• | Check for poor connection at the BCM. Inspect the harness connectors for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals and poor terminal to wire connection (terminal crimped over wire insulation and not conductors).

• | Inspect the wiring harness for damage. Check for broken or chaffed insulation.

• | If the fault is suspected to be intermittent, wiggling the harness wiring may help in locating the fault.

### B0285