The rear fog lamp relay is supplied with battery voltage at all times from the REAR FOG fuse located in the rear fuse block. The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The body control module (BCM) energizes the rear fog lamp relay by applying ground to the rear fog lamp relay control circuit. When the rear fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the REAR FOG fuse to the rear fog lamp supply voltage circuit which illuminates the rear 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

Ignition ON, headlamps ON, verify the scan tool rear fog lamp switch parameter changes between ON and OFF when turning the rear fog lamp switch ON and OFF.

Rear Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connectors at the headlamp switch.
2. Test for less than 5.0 ohms between the ground circuit terminal C X1 and ground.

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

3. Ignition ON, verify the scan tool Rear Fog Lamp switch parameter is OFF.

⇒	If not the specified value, test the signal circuit terminal B X2 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 B X2 and the ground circuit terminal C X1. Verify the scan tool Rear Fog Lamp Switch parameter is OFF.

⇒	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 headlamp switch.

Rear Fog Lamp Malfunction

1. Ignition OFF, disconnect the rear fog lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the rear fog lamp control circuit terminal 87 and ground.

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

3. 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 terminal for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit terminal for a short to ground or an open/high resistance.

5. Disconnect the harness connector at the inoperative rear fog lamp.
6. Test for less than 5.0 ohms between the rear fog lamp ground circuit terminal E and ground.

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

7. Ignition OFF, connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87..
8. Connect a test lamp between the control circuit terminal C and ground. Verify the test lamp illuminates.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage.

9. If all circuits test normal, replace the rear fog lamp relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.