Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Rear Defogger Battery Supply | 1 | 1 | -- | -- |
Rear Defogger Relay Control | B0283 06 | B0283 06 | 2 | -- |
Rear Defogger Element Supply | 1 | 1 | 2 | -- |
Rear Defogger Relay Coil Ground | -- | B0283 06 | -- | -- |
Rear Defogger Element Ground | -- | 1 | -- | -- |
1. Rear Defogger Inoperative 2. Rear Defogger Always ON | ||||
Circuit/System Description
The HVAC control module controls the rear window defroster through the REAR DEFOG relay located in the underhood fuse block. When the rear defroster is activated the HVAC control module supplies battery voltage through the defroster relay control circuit to energize the relay coil.
Reference Information
Schematic Reference
Connector End View Reference
Window Systems Connector End Views
Description and Operation
Rear Window Defogger Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition ON, verify that the rear defogger indicator illuminates when the switch is activated.
- Connect a test lamp from the supply side of the REAR DEFOG fuse to ground.
- Verify that the test lamp is illuminated while the rear defogger is turned on.
- Disconnect the rear defogger grid connectors and verify that a test lamp illuminates when connected from battery voltage to the ground circuit connector.
- Connect a test lamp across the rear defogger grid connectors and verify that the test lamp illuminates when the defogger is turned on.
- If the circuits test normal replace the rear window defogger grid.
| ⇒ | If the indicator does not illuminate when system operation is attempted, replace the HVAC control module. |
| ⇒ | If the test lamp does not illuminate test the battery supply circuit to the REAR DEFOG relay for an open/high resistance or short to ground. If the circuit tests normal replace the REAR DEFOG relay. |
| ⇒ | If the test lamp does not illuminate repair the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate repair the defogger grid supply circuit for an open/high resistance. |
Component Testing
Rear Window Defogger Grid Test
- Ignition ON, turn on the rear window defogger.
- Verify that a test lamp illuminates between each rear window defogger grid line and ground.
| ⇒ | If the test lamp remains bright at the middle of the grid line, test for an open between the test point and the ground side of the grid. |
| ⇒ | If the test lamp remains off at the middle of the grid line, test for an open between the test point and the voltage supply side of the grid. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for HVAC control module replacement, programming, and setup |
