Circuit/System Testing
- Ignition OFF, disconnect the REAR DEFOG relay.
- Test for less than 10 Ω between the ground circuit terminal 85 and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify a test lamp does not illuminate between the control circuit terminal 87 and ground.
- If the test lamp illuminates, test the control circuit for a short to voltage.
- Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
- If the test lamp does not illuminate, replace the underhood fuse block.
- Ignition OFF, disconnect the X2 harness connector at the rear window defogger grid.
- Test for less than 10 Ω between the ground circuit terminal A and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
- Connect the X2 harness connector at the rear window defogger grid.
- Ignition ON, connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the rear window defogger grid is activated.
- If the rear window defogger grid does not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, refer to Defogger Grid Lines Diagnosis .
- Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
- Engine running, command the Rear Defog Request ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
- If all circuits test normal, test or replace the REAR DEFOG relay.