Front Fog Lamps Malfunction (V8)
Front Fog Lamps Malfunction (V8)
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 vehicle fog lamps are controlled by the body control module (BCM) based on an input from the fog lamp switch. The fog lamp switch is a momentary switch located on the multifunction turn signal lever. When activated, the fog lamp switch provides a momentary ground to the BCM via the front fog lamp switch signal circuit, indicating the fog lamps are requested ON.
The BCM controls the fog lamps based on the inputs explained above. When a fog lamp request is received, the BCM grounds the fog lamp relay control circuit. This energizes the FOG LPS PCB relay. With the relay energized, B+ is applied to both fog lamps.
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. Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while cycling the fog lamp switch between the On and Off positions. The parameter should cycle between On and Off.
• If the parameter does not cycle between the specified values, refer to Fog Lamp Switch Circuit Malfunction.
2. Command the fog lamps ON and OFF with a scan tool. Verify the fog lamps turn ON and OFF when changing between the commanded states.
• If the fog lamps do not cycle between the commanded states, refer to Fog Lamp Circuit Malfunction.
Circuit/System Testing
Fog Lamp Switch Circuit Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the multifunction turn signal lever.
2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal 3 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 4 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 4 and the ground circuit terminal 3. 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 and open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the multifunction turn signal lever.
Fog Lamp Circuit Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the underhood fuse block.
2. Connect a test lamp between the control circuit terminal H5 and B+.
3. Ignition ON, 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 underhood fuse block. Disconnect the harness connector at the appropriate fog lamp
5. Test for less than 10 ohms of resistance between the ground circuit terminal B 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 A 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 underhood fuse block.
• 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, replace the underhood fuse block.
• 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 appropriate fog lamp bulb.
8. If all circuits test normal, test or replace the appropriate fog lamp bulb.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Fog Lamp Bulb Replacement (GXP) (Service and Repair)
* Turn Signal Multifunction Switch Replacement (Turn Signal Multifunction Switch Replacement)
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Control Module References (Programming and Relearning)for BCM replacement, setup, and programming