B0286

DTC B0285 or B0286

Circuit Description

The body control module (BCM) monitors the rear defogger switch input. When the rear defogger is turned ON, the rear defog switch is closed and the BCM supplies the battery positive voltage to the coil side of the rear defog relay. This will energize the relay activating the rear defogger.

The first time that the rear defogger is activated in an ignition cycle, the rear defogger will remain ON for 10 minutes, or until the ignition switch is turned OFF. If the rear defogger is activated again during the same ignition cycle, the rear defogger will remain ON for 5 minutes, or until the ignition switch is turned OFF.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B0285 Electronic Rear Defrost Circuit Low
* DTC B0286 Electronic Rear Defrost Circuit High

Conditions for Running the DTC

The ignition is in RUN.

Conditions for Setting the DTC

* The BCM detects an open, short to ground, or short to voltage in the rear defog relay control circuit.
* The condition exists for 30 seconds.
* The BCM is not requesting the Rear Defogger System.

Action Taken When the DTC Sets

* The rear window defogger will be inoperative if the circuit is open or shorted to ground.
* The rear window defogger will be ON if the circuit is shorted to voltage.
* The rear defogger indicator may not illuminate when the rear defogger switch is activated or may always be illuminated.

Conditions for Clearing the DTC

* This DTC will change from current to history when the fault is no longer present.
* A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Test Description

Step 1 - Step 11:

The numbers below refer to the step numbers on the diagnostic table.
2. Listen for an audible click when the rear defog relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
3. This step verifies that the BCM is providing battery positive voltage input to the rear defog relay.
5. This step tests for a short to ground, or short to voltage on the rear defog relay control circuit of the rear defog relay coil.