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 fog lamp relay is supplied with battery voltage at all times via the FOG LAMP fuse. The fog lamp switch signal circuit is grounded momentarily by pressing the fog lamp switch. The body control module (BCM) energizes the fog lamp relay by applying voltage to the fog lamp relay control circuit. When the fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FOG LAMP fuse to the fog lamp control circuit which illuminates the fog lamps.
Reference Information
Schematic Reference
Fog Lights Schematics (Electrical 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 (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
Programming and Relearning (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Front Fog Lamp Switch parameter while activating the front fog lamp switch. The parameter should change between Active and Inactive.
• If the parameter does not change between the commanded states, refer to Fog Lamp Switch Malfunction.
2. Activate the front fog lamp switch and observe the fog lamps. The fog lamps should illuminate.
• If the front fog lamps do not illuminate, refer to Fog Lamps Malfunction.
Circuit/System Testing
Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the fog lamp switch.
2. Ignition OFF, verify a test lamp illuminates between B+ and the ground circuit terminal A.
• 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 C 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 C and ground. 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.
5. If all circuits test normal, test or replace the fog lamp switch.
Fog Lamps Malfunction
1. Ignition OFF, disconnect the fog lamp relay.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal 85 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. 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.
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 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. If the circuit tests normal, test or replace the fog lamp relay.
5. Disconnect the harness connector at the inoperative fog lamp.
6. Ignition OFF, exterior lamps OFF, test for less than 5 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 illuminate.
• If the fog lamps do not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the inoperative fog lamp.
9. Connect a test lamp between the control circuit terminal 86 and ground.
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 voltage. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the BCM.
11. If all circuits test normal, test or replace the fog lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fog Lamp Switch Replacement (Service and Repair)
* Front Fog Lamp Replacement (Removal and Replacement)
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup, and programming