Circuit/System Testing

Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the fog lamp switch.
2. Ignition OFF, verify a test lamp illuminates between B+ and the ground circuit terminal A.
   • If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Front Fog Lamp Switch parameter is Inactive.
   • If not the specified value, test the signal circuit terminal C for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the signal circuit terminal C and ground. Verify the scan tool Front Fog Lamp Switch parameter is Active.
   • If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the fog lamp switch.

Fog Lamps Malfunction

1. Ignition OFF, disconnect the fog lamp relay.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 85 and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that 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.
4. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
   • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground. If the circuit tests normal, test or replace the fog lamp relay.
5. Disconnect the harness connector at the inoperative fog lamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the inoperative fog lamp.
8. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the fog lamps illuminate.
   • If the fog lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the inoperative fog lamp.
9. Connect a test lamp between the control circuit terminal 86 and ground.
10. Command the Fog Lamps 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 BCM.
    • If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
11. If all circuits test normal, test or replace the fog lamp relay.