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 front fog lamp relay is supplied with battery voltage at all times. The front fog lamp switch signal circuit is grounded momentarily by pressing the front fog lamp switch. The body control module (BCM) energizes the front fog lamp relay by applying ground to the front fog lamp relay control circuit. When the front fog lamp relay is energized, the relay switch contacts close and battery voltage is applied through the FOG LAMP fuse to the front fog lamp control circuit which illuminates the front fog lamps.
Reference Information
Schematic Reference
Fog Lights Schematics (Fog Lights Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
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 Front Fog Lamps Switch parameter while turning the front fog lamps switch ON and OFF. The parameter should change between Active and Inactive.
• If the parameter does not change between the commanded states, refer to Front Fog Lamp Switch Malfunction.
2. Observe the scan tool Front Fog Lamps Relay Command parameter while turning the front fog lamps switch ON and OFF. The parameter should change between Active and Inactive.
• If the parameter does not change between the commanded states, refer to Front Fog Lamps Malfunction.
3. Command the All Indicators Test ON and OFF with a scan tool. The font fog lamps indicator should turn ON and OFF when changing between the commanded states.
• If the front fog lamps indicator illuminates during the test, replace the K9 BCM.
• If the front fog lamps indicator does not illuminate during the test or remains illuminated at all times, replace the P16 instrument cluster.
Circuit/System Testing
Front Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition ON, verify that a test lamp illuminates between the 12 V reference circuit terminal 1 and ground.
• If the test lamp does not illuminate, test the 12 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal and the circuit fuse is open, test the signal circuit terminal 12 for a short to ground.
3. Verify the scan tool Front Fog Lamps Switch parameter is Inactive.
• If not the specified value, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 BCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 12 V reference circuit terminal 1. Verify the scan tool Front Fog Lamps Switch parameter is Active.
• If not the specified value, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the S30 headlamp switch.
Front Fog Lamps Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the X50A underhood fuse block.
2. Connect a test lamp between the control circuit terminal 19 and B+.
3. Command the Front Fog Lamps Command 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 K9 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 K9 BCM.
4. Ignition OFF, connect the X2 harness connector at the X50A underhood fuse block. Disconnect the harness connector at the appropriate E29 Fog Lamp - Front.
5. Test for less than 5 ohm between the 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.
• If greater than the specified range, test the ground circuit for an open/high resistance.
7. Command the Front Fog Lamps Command 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 E29 Fog Lamp - Front.
• 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 E29 Fog Lamp - Front.
• 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 E29 Fog Lamp - Front.
8. If all circuits test normal, test or replace the X50A underhood fuse block.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Fog Lamp Replacement (Base/SS) (Removal and Replacement)
* Accessory Wiring Junction Block Retainer Replacement (Removal and Replacement)
* Headlamp, Instrument Panel Lamp Dimmer, and Fog Lamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM and instrument cluster replacement, setup, and programming