Front Fog Lamps Malfunction
Front Fog Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The body control module (BCM) controls the fog lamps based on inputs from the fog lamp switch. When the fog lamp switch is pressed, a ground path is provided on the front fog lamp switch signal circuit to the BCM, indicating the front fog lamps ON command. In response to this signal, the BCM grounds the fog lamp relay control circuit energizing the FOG LAMP PCB Relay. With the fog lamp relay energized, battery voltage is applied through the FOG Fuse and the fog lamp supply voltage circuits illuminating the front fog lamps.
When a fog lamp request is seen by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the fog lamp indicator be illuminated.
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 (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Front Fog Lamps 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 Malfunction.
2. Observe the front fog lamps while pressing and releasing the front fog lamp switch. The front fog lamps should turn ON and OFF.
• If the front fog lamps do not turn ON and OFF as selected, refer to Fog Lamps Malfunction.
3. Command the Display Test ON and OFF with a scan tool. The fog lamps indicator should turn ON and OFF when changing between the commanded states.
• If the fog lamps indicator illuminates during the test, replace the BCM.
• If the fog lamps indicator does not illuminate during the test or remains illuminated at all times, replace the instrument cluster.
Circuit/System Testing
Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Verify that a test lamp illuminates between the ground circuit terminal 8 and B+.
• 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 6 for a short to ground. If the circuit tests normal, replace the BCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 6 and the ground circuit terminal 8. 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 Lamps Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the fuse block - underhood.
2. Connect a test lamp between the control circuit terminal K5 and B+.
3. 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.
4. Ignition OFF, connect the X2 harness connector at the fuse block - underhood. Disconnect the harness connector at the appropriate fog lamp.
5. Test for less than 5 ohm between the fog lamp ground circuit terminal A and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal B and ground.
7. 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 voltage. If the circuit tests normal, replace the fuse block - underhood.
• If the test lamp is always OFF and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the fuse block - underhood.
• If the test lamp is always OFF and the circuit fuse is open, test the control circuit for a short to ground. If the circuit tests normal, test or replace the fog lamp.
8. If all circuits test normal, test or replace the fog lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Switch Replacement (Service and Repair)
* Front Fog Lamp Bulb Replacement (Service and Repair)
* Underhood Electrical Center or Junction Block Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming