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
The front fog lamp relay coil is supplied with battery voltage when the ignition is in the RUN or CRANK position. The front fog lamp relay switch is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) energizes the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FRONT FOG fuse to the front fog lamp control circuit which illuminates the front fog lamps.
Reference Information
Schematic Reference
Fog Lights Schematics (Fog Lights Schematics)
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
Ignition ON, headlamps ON, verify the scan tool front fog lamp switch parameter changes between ON and OFF when turning the front fog lamp switch ON and OFF.
If the scan tool parameter does not change between ON and OFF, refer to the Fog Lamp Switch Malfunction.
If the switch operates normal but the front fog lamps do not turn ON and OFF, refer to the Fog Lamp Malfunction.
Circuit/System Testing
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 Front Fog Lamp Switch parameter is OFF.
• If not the specified value, test the signal circuit terminal A 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 A X2 and the ground circuit terminal C X1. 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 an 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 Malfunction
1. Ignition OFF, disconnect the front fog lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the front 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 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 terminal 87 for a short to ground.
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. Disconnect the harness connector at the inoperative front fog lamp.
6. Test for less than 5.0 ohms between the front fog lamp ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect a test lamp between the control circuit terminal A and ground.
8. Ignition OFF, connect a 15A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. 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 front fog lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Fog Lamp Bulb Replacement (Service and Repair)
* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup