Front Fog Lamps Malfunction
Front Fog Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
With both the ignition switch in the ON position and the park lamps or low beam head lamps ON, the fog lights will illuminate when the driver presses the fog lamp switch. The FRONT FOG fuse in the underhood fuse block supplies battery positive voltage to the FRONT FOG relay. With the headlamp switch is in either the park or headlamp position and the fog lamp switch is pressed, the body control module (BCM) will energize the FRONT FOG relay control circuit. The current flow is from the FRONT FOG relay to both front fog lamps and to ground. The state of the fog lamps, either ON or OFF, will remain the same until the fog lamp switch is pressed again, or the ignition switch is cycled OFF and ON. Fog lamp operation will be cancelled whenever the park lamps are turned OFF or the high beam headlights have been selected.
Reference Information
Schematic Reference
Fog Lights Schematics (Fog Lights Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Observe the scan tool Front Fog Lamp Switch parameter while pressing and releasing the fog lamp switch. The parameter should change between Active and Inactive.
• If the parameter does not change between the specified values, Refer to Fog Lamp Switch Circuit Test.
2. Ignition ON, command the fog lamps ON and OFF with a scan tool. Observe the fog lamps turn on and off.
• If the fog lamps do not turn on and off, Refer to Fog Lamp Relay Circuit Test.
3. With the fog lamps ON, verify the fog lamp indicator is illuminated on the IPC.
• If the indicator does not illuminate, Refer to Front Fog Lamp Indicator Test.
Circuit/System Testing
Fog Lamp Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 4.
• 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 1 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 1 and the ground circuit terminal 4. 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 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 Relay Circuit Test
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 86 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 for a short to ground. If the circuit tests normal, test or replace the FOG LAMP relay.
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 an open/high resistance.
5. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
6. 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.
7. Connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
8. Disconnect the harness connector at the appropriate fog lamp.
9. Verify that a test lamp illuminates between the fog lamp control circuit terminal A and ground.
• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.
10. Verify that a test lamp illuminates between the fog lamp ground circuit terminal B and B+.
• If the test lamp does not illuminate, test the ground circuit for a open/high resistance.
11. If all circuits test normal, test or replace the FOG LAMP relay.
Front Fog Lamp Indicator Test
1. Ignition ON, with a scan tool perform the IPC Display Test. Verify the fog lamp indicator illuminates.
• If the front fog lamp indicator does not illuminate during the test or remains illuminated at all times, replace the IPC.
2. If all circuit test normal, replace the BCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Headlamp Switch Replacement (Service and Repair)
* Front Fog Lamp Bulb Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM or IPC replacement, setup, and programming