B0285

Schematic:

CIRCUIT DESCRIPTION
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 defrost relay providing power to circuit 293 (rear defrost heater elements), circuit 683 (heated mirror relay coil) and circuit 683 (rear defrost LED telltale). Momentarily switching circuit 292 to ground again will result in the BCM turning the rear defrost relay "OFF."

The first time in an ignition cycle that the rear defrost is activated, rear defrost is activated, rear defrost will remain "ON" for 15 minutes or until the ignition switch is turned "OFF." If rear defrost is activated again during the same ignition cycle, rear defrost will remain "ON" for 7 1/2 minutes or until the ignition switch is turned "OFF."

DTC PARAMETERS
^ Ignition in RUN
^ Circuit 193 grounded
^ BCM is NOT requesting the rear defrost system
^ Condition exists for 30 seconds

DIAGNOSTIC AIDS:
^ Check for poor connection at the BCM. Inspect 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 wiring harness for damage. Check for broken or chaffed insulation.
^ If fault is suspected to be intermittent, wiggling harness wiring may help in locating fault.

TEST DESCRIPTION

Diagnostic Chart: