Diagnostic Routine E
Diagnostic Routine E
Diagnostic Overview
The Defrost System is Inoperative
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
Visual Inspection and Diagnostic Pre-checks
- Verify that BJB (Battery Junction Box) fuse 9 (30A) and 23 (5A) are OK.
- Visually inspect the rear window defrost relay.
- Visually inspect the rear window defrost grid and electrical connectors for damage.
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 THE REAR WINDOW DEFROST GRID VOLTAGE
1. Ignition OFF.
2. Disconnect: Rear Window Defrost Grid C402A (2-door) or Isolator C4221 (4-door).
3. Start the engine.
4. Activate the rear window defrost switch.
5. Measure:
Is the voltage greater than 11 volts?
3. CHECK THE REAR WINDOW DEFROST GRID GROUND
1. Ignition OFF.
2. Disconnect: Rear Window Defrost Grid C402B.
3. Measure:
Is the resistance less than 3 ohms?
4. CHECK THE REAR WINDOW DEFROST LED (Light-emitting Diode) CIRCUIT FOR A SHORT TO GROUND
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Disconnect: Defrost Switch.
4. Measure:
Is the resistance greater than 10,000 ohms?
5. CHECK THE REAR WINDOW DEFROST LED (Light-emitting Diode) CIRCUIT OPERATION
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Connect a fused jumper wire:
Is the rear window defrost switch LED (Light-emitting Diode) illuminated?
6. CHECK THE REAR WINDOW DEFROST LED (Light-emitting Diode) CIRCUIT FOR AN OPEN
1. Disconnect: Defrost Switch.
2. Measure:
Is the resistance less than 3 ohms?
7. CHECK THE REAR WINDOW DEFROST SWITCH GROUND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
8. CHECK THE VOLTAGE TO THE REAR WINDOW DEFROST RELAY
1. Ignition OFF.
2. Disconnect: Rear Window Defrost Relay.
3. Ignition ON.
4. Measure:
Is the voltage greater than 11 volts for both measurements?
9. CHECK THE BCM (Body Control Module) OUTPUT
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. Start the engine.
2. Activate the rear window defrost switch.
3. Measure:
Does the test light illuminate?
10. CHECK THE REAR WINDOW DEFROST RELAY
1. Ignition OFF.
2. Carry out the rear window defrost relay component test.
Did the rear window defrost relay pass the component test?
11. CHECK THE REAR DEFROST SWITCH (R_DEFRST_SW) PID (Parameter Identification)
1. Using a scan tool, view BCM (Body Control Module) PIDs (Parameter Identifications).
2. Monitor the BCM (Body Control Module) PID (Parameter Identification) R_DEFRST_SW while pressing and releasing the rear window defrost switch.
Does the PID (Parameter Identification) status change when the rear window defrost switch is pressed and released?
12. CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280B.
3. Measure:
Is the resistance less than 3 ohms?
13. CHECK THE BCM (Body Control Module) DEFROST SWITCH INPUT
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. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Activate the rear window defrost switch while observing the test light.
4. Measure:
Does the test light illuminate when the rear window defrost switch is pressed?
14. CHECK THE REAR WINDOW DEFROST SWITCH GROUND CIRCUIT FOR AN OPEN
1. Disconnect: Defrost Switch.
2. Measure:
Is the resistance less than 3 ohms?
15. CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
16. CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR A SHORT TO GROUND
1. Ignition OFF.
2. Disconnect: BCM (Body Control Module) C2280C.
3. Measure:
Is the resistance greater than 10,000 ohms?
17. CHECK THE REAR WINDOW DEFROST SWITCH CIRCUIT FOR A SHORT TO GROUND WITH THE SWITCH DISCONNECTED
1. Disconnect: Defrost Switch.
2. Measure:
Is the resistance greater than 10,000 ohms?
18. CHECK THE REAR WINDOW DEFROST RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Ignition OFF.
2. Disconnect: Rear Window Defrost Relay.
3. Disconnect: BCM (Body Control Module) C2280B.
4. Ignition ON.
5. Measure:
Is any voltage present?
19. 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?
