Diagnostic Routine F

Diagnostic Routine F

Diagnostic Overview

The Defrost System Does Not Shut Off Automatically

Refer to Wiring Diagram Set 56 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

REFER to Rear Window Defrost .

DTC Fault Trigger Conditions






Special Tool(s)






Pinpoint Test

1. CHECK FOR BCM (Body Control Module) DTCs (Diagnostic Trouble Codes)

1. Ignition ON.

2. Using a scan tool, perform BCM (Body Control Module) self-test.

Are any BCM (Body Control Module) DTCs (Diagnostic Trouble Codes) present?







2. CHECK FOR A SHORT TO VOLTAGE IN THE DEFROST SWITCH LED (Light-emitting Diode) CIRCUIT

1. Ignition OFF.

2. Disconnect: Defrost Switch.

3. Disconnect: BCM (Body Control Module) C2280C.

4. Ignition ON.

5. Measure:





Is any voltage present?







3. CHECK FOR A SHORT TO VOLTAGE IN THE DEFROST GRID CIRCUIT

1. Ignition OFF.

2. Disconnect: Rear Window Defrost Relay.

3. Ignition ON.

4. Measure:





Is any voltage present?







4. CHECK FOR A SHORT TO GROUND IN THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT

NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning of this system. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.

1. Measure:





Does the test light illuminate?







5. CHECK FOR A SHORT TO GROUND IN THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT WITH THE BCM (Body Control Module) DISCONNECTED

1. Ignition OFF.

2. Disconnect: Rear Window Defrost Relay (if not previously disconnected).

3. Disconnect: BCM (Body Control Module) C2280B.

4. Measure:





Is the resistance greater than 10,000 ohms?







6. CHECK FOR CORRECT BCM (Body Control Module) OPERATION

1. Ignition OFF.

2. Inspect the BCM (Body Control Module) connectors.

3. Repair:

- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins as necessary
- pushed-out-pins - install new pins as necessary

4. Reconnect the BCM (Body Control Module) connectors and all previously disconnected rear window defrost system connectors. Make sure they seat and latch correctly.

5. Operate the system and determine if the concern is still present.

Is the concern still present?