Circuit/System Testing

Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the fog lamp switch.
2. Ignition OFF, verify that 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 X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal C3 and ground.
3. 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 an open/high resistance. If the circuit tests normal, replace the BCM.
4. Ignition OFF, connect the X2 harness connector at the underhood fuse block.
5. Disconnect the X3 harness connector at the underhood fuse block.
6. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal F2 and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the X3 harness connector at the underhood fuse block.
8. Disconnect the harness connector at the inoperative fog lamp.
9. 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.
10. Connect a test lamp between the control circuit terminal A and ground.
11. 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 underhood fuse block.
    • If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
    • If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.
12. If all circuits test normal, replace the inoperative fog lamp.