B106B

B106B,B106D-REAR DEFROST CONTROL CIRCUIT LOW/OPEN - FCM





For a complete wiring diagram refer to Diagrams/Electrical.

- When Monitored:

Continuously

- Set Condition:

When the Front Control Module does not detect voltage on the Defogger Relay Control circuit.

1





Diagnostic Test

With the scan tool, record and erase DTC's

Operate the Rear Defogger Switch several times.

Cycle the ignition from on to off 3 times and leave on.

With the scan tool, read DTC's.

Does the scan tool display the same DTC?

Yes

- Go To 2

No

- The conditions that caused this code to set are not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2.JUNCTION BLOCK FUSE

Turn the ignition on.

Using a 12-volt test light connected to ground, check the Rear Window Defogger fuse in the Junction Block.

Does the test light illuminate and was the fuse OK?

No

- Repair the Ignition Switch Output (Run) circuit for an open or replace the fuse if open and check for a shorted Defogger Relay.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

Yes

- Go To 3

3.OPEN IGNITION SWITCH OUTPUT (RUN) TO RELAY





Remove the Rear Defogger Relay from the Junction Block.

Using a 12-volt test light connected to ground, check the Ignition Switch Output circuit at the relay connector.

Does the test light illuminate?

No

- Replace the Junction Block.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

Yes

- Go To 4

4.REAR WINDOW DEFOGGER RELAY

Install a known good relay in place of the Rear Window Defogger Relay.

With the scan tool erase DTC's

Operate the Rear Window Defogger several times.

Cycle the ignition from on to off 3 times and leave on.

With the scan tool, read DTC's.

Does the scan tool display the same DTC?

No

- Replace the original Rear Window Defogger Relay.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

Yes

- Go To 5

5.CHECK THE (C115)DEFOGGER RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND





Remove the Rear Window Defogger Relay from the junction block.

Disconnect the Front Control Module from the PDC 49 - way connector.

Measure the resistance between ground and the (C115) Defogger Relay Control circuit at the relay.

Is the resistance below 1000.0 ohms?

Yes

- Repair the (C115) Defogger Relay Control circuit for a short to ground.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

No

- Go To 6

6.CHECK THE (C115) DEFOGGER RELAY CONTROL CIRCUIT FOR AN OPEN





Measure the resistance of the (C115) Defogger Relay Control circuit from the relay connector to FCM connector.

Is the resistance below 3.0 ohms?

Yes

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

No

- Repair the (C115) Defogger Relay Control circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test