Circuit Description
The body control module (BCM) controls the rear defogger relay. Battery voltage for the relay coil is supplied through the HVAC fuse through circuit 41. The BCM grounds circuit 193 when the rear defogger switch is pressed in order to engage the relay.
Conditions for Running the DTC
The ignition switch is on.
Conditions for Setting the DTC
The rear defogger control circuit is open or shorted to ground for 5 seconds.
Action Taken When the DTC Sets
| • | If the rear defogger control circuit is open, the rear defogger is inoperative. |
| • | If the rear defogger control circuit is shorted to ground, the rear defogger will be on all the time with the ignition switch on. |
Conditions for Clearing the DTC
| • | A current DTC B0285 will clear when the malfunction is no longer present. |
| • | All BCM history codes will clear after 100 ignition cycles with no current codes active during the 100 ignition cycles. |
Diagnostic Aids
Try performing the tests while wiggling the wiring and connectors. This may often cause the malfunction to appear.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
Listen for an audible click when the rear defogger relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
-
Tests for voltage at the coil side of the rear defogger relay. The HVAC fuse supplies power to the coil side of the rear defogger relay.
-
Verifies that the body control module is providing ground to the rear defogger relay.
-
Tests if ground is constantly being applied to the rear defogger relay.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Stationary Windows Diagnostic System Check? | Go to Step 2 | Go to A Diagnostic System Check-Stationary Windows |
Does the rear defogger relay turn ON and OFF with each command? | Go to Testing for Intermittents and Poor Connections in Wiring Systems | Go to Step 3 | |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 10 | |
Does the test lamp turn ON and OFF with each command? | Go to Step 8 | Go to Step 5 | |
Does the test lamp remain illuminated with each command? | Go to Step 7 | Go to Step 6 | |
6 | Test the control circuit of the rear defogger relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
7 | Test the control circuit of the rear defogger relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Inspect for poor connections at the rear defogger relay. Refer to Testing for Intermittents and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the body control module. Refer to Testing for Intermittents and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
10 | Repair the coil side feed circuit of the rear defogger relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- |
11 | Replace the rear defogger relay. Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the body control module. Refer to Body Control Module Replacement in Body Control System. Important: Perform the set up procedure for the body control module. Refer to BCM Programming/RPO Configuration in Body Control System. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
