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 rear fog lamp relay is supplied with battery voltage at all times. The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The instrument panel module (IPM) sends a serial data message to the rear integration module (RIM) which energizes the rear fog lamp relay by applying ground to the rear fog lamp relay control circuit. When the rear fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the REAR FOG LAMP fuse to the rear fog lamp supply voltage circuit which illuminates the rear 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)
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 Rear Fog Lamp Relay Command parameter while activating the rear fog lamp switch. The parameter should change between ON and OFF.
• If the parameter does not change between the commanded states, refer to Rear Fog Lamp Switch Malfunction.
2. Turn the rear fog lamps ON and OFF with the rear fog lamps switch. The rear fog lamps should turn ON and OFF as selected.
• If the rear fog lamps do not change between the selected states, refer to Rear Fog Lamps Malfunction.
3. Command the Display Test ON and OFF with a scan tool. The rear fog lamps indicator should turn ON and OFF when changing between the commanded states.
• If the rear fog lamps indicator illuminates during the test, replace the rear integration module.
• If the rear fog lamps indicator does not illuminate during the test or remains illuminated at all times, replace the instrument cluster.
Circuit/System Testing
Rear Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the ground circuit terminal 3.
• If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp does not illuminate between B+ and the signal circuit terminal 2.
• If the test lamp illuminates, test the signal circuit for a short to ground. If the circuit tests normal, replace the IPM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the ground circuit terminal 3. Verify the rear fog lamps are illuminated.
• If the rear fog lamps do not illuminate, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPM.
5. If all circuits test normal, test or replace the turn signal/multifunction 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 R35 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 R32 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 R32 for a short to ground. If the circuit tests normal, test or replace the rear fog lamp relay.
4. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal R31 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 rear fog lamp.
6. Ignition OFF, scan tool 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 rear fog lamp.
8. Connect a 15 A fused jumper wire between the B+ circuit terminal R32 and the control circuit terminal R33. Verify the rear fog lamps are activated.
• If the rear fog lamps do not activate, test the control circuit terminal R33 for an open/high resistance. If the circuit tests normal, test or replace the inoperative rear fog lamp.
9. Connect a test lamp between the B+ circuit terminal R31 and the control circuit terminal R35
10. Command the Rear Fog lamps ON and OFF with the 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 RIM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the RIM.
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.
* Underhood Electrical Center or Junction Block Replacement (Removal and 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))
* Turn Signal Multifunction Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for IPM, IPC, or RIM replacement, setup, and programming