The vehicle fog lamps are controlled by the body control module (BCM) based on an input from the fog lamp switch. The fog lamp switch is a momentary switch integrated with the headlamp switch. When activated, the fog lamp switch provides a momentary ground to the BCM via the front fog lamp switch signal circuit, indicating the fog lamps are requested ON.

The BCM controls the fog lamps based on the inputs explained above. When a fog lamp request is received, the BCM grounds the fog lamp relay control circuit. This energizes the FOG LP relay. With the relay energized, B+ is applied to both fog lamps.

Schematic Reference

Fog Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information

1. Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while cycling the fog lamp switch between the On and Off positions. The parameter should cycle between On and Off.

⇒	If the parameter does not cycle between the specified values, refer to Fog Lamp Switch Circuit Malfunction.

2. Command the fog lamps ON and OFF with a scan tool. Verify the fog lamps turn ON and OFF when changing between the commanded states.

⇒	If the fog lamps do not cycle between the commanded states, refer to Fog Lamp Circuit Malfunction.

Fog Lamp Switch Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, test for less than 10 ohms of resistance between the ground circuit terminal 17 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Front Fog Lamp Switch parameter is Off.

⇒	If not the specified value, test the signal circuit terminal 7 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 7 and the ground circuit terminal 17. Verify the scan tool Front Fog Lamp Switch parameter is On.

⇒	If not the specified value, test the signal circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the headlamp switch.

Fog Lamp Circuit Malfunction

1. Ignition OFF, disconnect the FOG LPS relay.
2. Ignition ON, verify a test lamp does not illuminate between the control circuit terminal A9 and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify a test lamp illuminates between the B+ circuit terminal C9 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 FOG LPS fuse is open, test the control circuit terminal A9 for a short to ground. If the circuit tests normal, test or replace the FOG LP relay.

4. Verify a test lamp illuminates between the B+ circuit terminal C10 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Disconnect the harness connector at the applicable fog lamp.
6. Test for less than 10 ohms of resistance 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 appropriate fog lamp.
8. Connect a 10A fused jumper wire between the B+ circuit terminal C10 and the control circuit terminal A9. Verify the fog lamps are activated.

⇒	If the fog lamps do not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the applicable fog lamp bulb.

9. Connect a test lamp between the B+ circuit terminal C9 and the control circuit terminal A10.
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 ground. If the circuit tests normal, replace the BCM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

11. If all circuits test normal, test or replace the appropriate FOG LPS relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.