Rear Fog Lamps Malfunction
Rear 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 rear fog lamps based on inputs from the headlamp switch. When the rear fog lamp switch is pressed, a ground path is provided on the rear fog lamp switch signal circuit to the BCM, indicating the rear fog lamps ON command. In response to this signal, the BCM grounds the rear fog lamp relay control circuit energizing the Rear Fog Lamp Relay. With the rear fog lamp relay energized, battery voltage is applied through the RR FOG Fuse and the rear fog lamp control circuits illuminating the rear fog lamps.
Reference Information
Schematic Reference
Fog Lights Schematics Fog Lights Schematics
Connector End View Reference
Component Connector End Views A/C Compressor Clutch
Description and Operation
Exterior Lighting Systems Description and Operation Exterior Lighting Systems
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 Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Rear Fog Lamp Switch parameter while pressing and releasing the rear fog lamp switch. The parameter should change between Active and Inactive.
• If the parameter does not change between the selected states, refer to the Rear Fog Lamp Switch Malfunction.
2. Ignition ON, command the Rear Fog Lamps ON and OFF with a scan tool. Verify the rear fog lamps turn on and off.
• If the front fog lamps are always on or always off, refer to Rear Fog Lamps Malfunction.
Circuit/System Testing
Rear Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 5 ohms between the ground circuit terminal 8 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Rear Fog Lamp Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 10 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 10 and the ground circuit terminal 8. Verify the scan tool Rear 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 headlamp switch.
Rear Fog Lamps Malfunction
1. Ignition OFF, disconnect the rear 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 terminal 87 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. Disconnect the harness connector at the appropriate fog lamp rear.
6. Test for less than 5 ohms between the ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the fog lamp rear.
8. Connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the fog lamp rear is activated.
• If the fog lamp rear does not activate and the circuit fuse is good, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the fog lamp rear.
• If the fog lamp rear does not activate 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 rear.
9. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
10. Command the Rear 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.
11. If all circuits test normal, test or replace the rear fog lamp relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)
* Headlamp Switch Replacement Service and Repair
* Control Module References Control Module References for BCM replacement, programming, and setup