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 switch is an input to the body control module (BCM) and is contained in the headlamp switch assembly. The BCM supplies voltage to the front fog lamp switch via the front fog lamp and I/P dimmer switch B+ reference circuit. When the front fog lamp switch is pressed, voltage from the B+ reference circuit is pulled down through the front fog lamp switch resistor. The front fog lamp resistor is part of the resistor ladder that also provides the dimming signals for the I/P dimmer switches. The BCM receives the voltage signal through the front fog lamp and I/P dimmer switch signal circuit.
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 F48UA 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 Sunshade - Left (D6I)
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, headlamps ON, observe the scan tool Front Fog Lamps 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 Front Fog Lamp Switch Malfunction.
• If the parameter changes between the commanded states, refer to Front Fog Lamps Malfunction.
2. Observe the front fog lamp indicator on the instrument cluster while activating the front fog lamp switch ON and OFF. The front fog lamp indicator should turn ON and OFF as the switch is activated.
• If the indicator does not change between the commanded states, refer to Front Fog Lamp Indicator Malfunction.
Circuit/System Testing
Front Fog Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
2. Ignition ON, test for B+ between the B+ reference circuit terminal 1 and ground
• If less than the specified range, test the B+ reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
3. Verify the scan tool LED Backlight Dimming Command parameter is greater than 40%.
• If less than the specified range, test the signal circuit terminal 12 for a short to voltage. If the circuit tests normal, replace the K9 BCM.
4. Ignition OFF, install a 3 A fused jumper wire between the B+ reference circuit terminal 1 and the signal circuit terminal 12.
5. Ignition ON, verify the scan tool LED Backlight Dimming Command parameter is less than 30%.
• If greater than the specified range, test the signal circuit terminal 12 for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
6. If all circuits test normal, replace the S30 headlamp switch.
Front Fog Lamps Malfunction
1. Ignition OFF, disconnect the X2 harness connector at the X50A fuse block - underhood.
2. Connect a test lamp between the control circuit terminal 19 and B+.
3. Ignition ON, command the Front 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 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 Fuse Block - Underhood.
5. Disconnect the harness connector at the appropriate E29 fog lamp.
6. Ignition OFF, exterior lamps OFF, 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.
7. Connect a test lamp between the control circuit terminal B and ground.
8. Ignition ON, command the Front 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 X50A fuse block - underhood.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the X50A fuse block - underhood.
9. If all circuits test normal, test or replace the E29 fog lamp.
Front Fog Lamp Indicator Malfunction
1. Ignition ON, with a scan tool perform the Instrument Cluster All Indicators Test and observe the front fog lamp indicator.
• If the front fog lamp indicator illuminates during the test, replace the K9 BCM.
• If the front fog lamp indicator does not illuminate during the test or remains illuminated at all times, replace the P16 instrument cluster.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Headlamp Switch Replacement Service and Repair
* Front Fog Lamp Bulb Replacement Service and Repair
* Front Compartment Fuse Block Replacement Front Compartment Fuse Block Replacement
* Control Module References Control Module References for BCM or Instrument Cluster replacement, setup, and programming