Rear Defogger Relay Control Circuit Open/Shorted to Ground

REAR DEFOGGER RELAY CONTROL CIRCUIT OPEN/SHORT TO GROUND

Rear Defogger Relay Control Circuit Open/Short To Ground:

DIAGNOSTIC TEST

WHEN MONITORED
With the ignition on.

SET CONDITION
When the BCM detects no voltage on the Rear Window Defogger Control circuit due to an open or short to ground.

POSSIBLE CAUSES
- Junction block fuse 39
- Code active
- Relay open or shorted
- Junction block - rear window defogger relay control short to ground
- Fused ignition switch output circuit open
- Junction block - rear window defogger relay control open
- Body control module

DIAGNOSTIC TEST

1. CHECK TROUBLE CODE
Turn the ignition on.
With the scan tool, erase DTCs.
Attempt to operate the Rear Window Defogger.
With the scan tool, read DTCs.

Q: Does the scan tool display REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT OPEN/SHORT TO GROUND?

YES: Go To 2
NO: Problem is intermittent and not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors and repair as necessary. Ensure the relay is completely plugged in.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2. JUNCTION BLOCK FUSE 39
Check Junction Block fuse 39.

Q: Is the fuse open.

YES: Check for a short to ground and replace the Junction Block fuse.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3

3. FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
Turn the ignition on.
Using a 12-volt test light connected to ground, check the Fused Ignition Switch Output circuit at Fuse 39.
The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Q: Does the test light illuminate brightly?

YES: Go To 4
NO: Repair the open Fused Ignition Switch Output circuit as necessary.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

4. RELAY OPEN OR SHORTED
Remove the Rear Window Defogger Relay from the Junction Block.
Install fuse if previously removed.
Install a substitute relay in place of the Rear Window Defogger Relay.
With the scan tool, erase DTCs.
Attempt to operate the Rear Window Defogger.
With the scan tool, read DTCs.

Q: Does the scan tool display REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT OPEN/SHORT TO GROUND?

YES: Go To 5
NO: Replace the original relay.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

5. JUNCTION BLOCK - REAR WINDOW DEFOGGER RELAY CONTROL SHORT TO GROUND




Turn the ignition off.
Remove the Rear Window Defogger Relay from the Junction Block.
Remove the Body Control Module from the Junction Block.

NOTE: Ensure the Junction Block connectors are reconnected at this time.

Measure the resistance between ground and the Rear Window Defogger Relay Control circuit in the relay connector of the Junction Block.

Q: Is the resistance below 100.0 ohms?

YES: Replace the Junction Block.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 6

6. JUNCTION BLOCK - REAR WINDOW DEFOGGER RELAY CONTROL OPEN




Turn the ignition off.
Remove the Rear Window Defogger Relay from the Junction Block.
Remove the Body Control Module from the Junction Block.
Measure the resistance of the Rear Window Defogger Relay Control circuit between the Relay connector and the Junction Block - BCM connector.

Q: Is the resistance below 2.0 ohms?

YES: Go To 7
NO: Replace the Junction Block.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

7. BODY CONTROL MODULE
If there are no possible causes remaining, view repair.

Repair
Replace the Body Control Module.
Perform BODY VERIFICATION TEST - VER 1. Body Verification Test