The front fog lamp relay and front fog lamps are grounded at G105 at all times. When the body control module (BCM) is momentarily grounded when the front fog lamp switch is turned to the ON position. Battery voltage is then supplied to the coil side of the front fog lamp relay. The relay contacts now close supplying the front fog lamps with battery voltage turning them ON.

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, command the front fog lamps ON and OFF with a scan tool. The front fog lamps should turn ON and OFF.

⇒	If the fog lamps do not turn ON and OFF, refer to Fog Lamp Malfunction.

2. Ignition ON, observe the scan tool front fog lamp switch parameter while pressing the front fog lamp switch. The reading should change between inactive and active.

⇒	If not the specified value, refer to Fog Lamp Switch Malfunction

3. Ignition ON, command the front fog lamps ON and OFF with a scan tool. The front fog lamp indicator should turn ON and OFF.

⇒	If not the specified value, refer to Fog Lamp Indicator Malfunction

Fog Lamp Malfunction

1. Ignition OFF, disconnect the fog lamp relay.
2. 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.

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 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 for an open/high resistance.

5. Ignition OFF, disconnect the harness connector at the inoperative fog lamp.
6. Test for less than 5.0 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 are activated.

⇒	If the fog lamps do not activate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the inoperative fog lamp.

9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
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 fog lamp relay.

Fog Lamp Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
2. Ignition ON, verify the scan tool front fog lamp switch parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the BCM.

3. Install a 3A fused jumper wire between the signal circuit terminal 7 and the low reference circuit terminal 3. 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.

4. If all circuits test normal, test or replace the headlamp and panel dimmer switch.

Fog Lamp Indicator Malfunction

1. Ignition OFF, disconnect the harness connector at the headlamp and panel dimmer switch.
2. Ignition ON, headlamps ON, connect a test lamp between the indicator control circuit terminal 8 and ground. The test lamp should not be illuminated.

⇒	If the test lamp is illuminated, test the indicator control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

3. Command the front fog lamps ON with a scan tool. The test lamp should be illuminated.

⇒	If the test lamp is not illuminated, test the indicator control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.

4. If all the circuits test normal replace the headlamp and panel dimmer switch.

Relay Test

1. Ignition OFF, disconnect the front fog lamp relay.
2. Test for 70-100 ohms between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 85

•

30 and 86

•

30 and 87

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 10A fused jumper wire between relay terminal 85 and B+. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Fog Lamp Switch Test

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for infinite resistance between the signal terminal 7 and the low reference terminal 3.

⇒	If not the specified value, replace the headlamp switch.

3. Test for less than 5 ohms between the signal terminal 7 and the low reference terminal 3 while pressing the front fog lamp switch.

⇒	If greater than the specified range, replace the headlamp switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.