Buick Regal: Front Fog Lamps Malfunction

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

1. Front Fog Lamps Malfunction
2. Front Fog Lamp Switch Malfunction

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 front fog lamp fuse to the front fog lamp control circuit which illuminates the front fog lamps. With the front fog lamp switch activated the BCM sends a message via serial data to the instrument cluster requesting the instrument cluster to illuminate the front fog indicator.

Reference Information

Schematic Reference

Fog Lights Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification

1. Ignition ON, headlamps ON.

2. Verify the scan tool Front Fog Lamps Switch parameter changes between Active and Inactive while commanding the front fog lamps ON and OFF with the front fog lamp switch.

• If the parameter does not change

Refer to Circuit/System Testing - Front Fog Lamp Switch Malfunction.

• Go to next step: If the parameter changes

3. Verify the front fog lamps turn ON and OFF when commanding the Front Fog Lamps ON and OFF with a scan tool.

• If the front fog lamps do not turn ON and OFF

Refer to Circuit/System Testing - Front Fog Lamps Malfunction.

• Go to next step: If the front fog lamps turn ON and OFF

4. Verify the front fog lamp indicator on the instrument cluster turns ON and OFF while commanding the front fog lamps ON and OFF with the front fog lamp switch.

• If the front fog lamp indicator does not turn ON and OFF

Refer to Circuit/System Testing - Front Fog Lamp Indicator Malfunction.

• Go to next step: If the front fog lamp indicator turns ON and OFF

5. All OK.

Circuit/System Testing

Front Fog Lamp Switch Malfunction

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S30 Headlamp Switch. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 8 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Ignition ON.

4. Verify the scan tool Front Fog Lamps Relay Command parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 10 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • If infinite resistance, replace the K9 Body Control Module.

• Go to next step: If Inactive

5. Install a 3 A fused jumper wire between the signal circuit terminal 10 and ground.

6. Verify the scan tool Front Fog Lamps Switch parameter is Active.

• If not Active

1. Ignition OFF, disconnect the X3 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 10 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • Go to next step: If less than 1 V
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If Active

7. Test or replace the S30 Headlamp Switch.

Front Fog Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, remove the appropriate E29 Fog Lamp - Front. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 10 Ω between the ground circuit terminal 2 and ground.

• If 10 Ω or greater

1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, repair the open/high resistance in the ground connection.

• Go to next step: If less than 10 Ω

3. Connect a test lamp between the control circuit terminal 1 and ground, ignition ON.

4. Verify the test lamp does not turn ON and OFF when commanding the Front Fog Lamps ON and OFF with a scan tool.

• If the test lamp turns ON and OFF

Test or replace the E29 Fog Lamp - Front.

• Go to next step: If the test lamp does not turn ON and OFF

5. Ignition OFF, install the E29 Fog Lamp - Front. Disconnect the X2 harness connector at the X50A Fuse Block - Underhood, ignition ON.

6. Verify the front fog lamps do not illuminate.

• If the front fog lamps illuminate

1. Ignition OFF, remove both E29 Fog Lamp - Front, ignition ON.
2. Test for less than 1 V between the control circuit terminal C1 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.

• Go to next step: If the front fog lamps do not illuminate

7. Ignition OFF, connect a 3 A fused jumper between the control circuit terminal C1 and B+, ignition ON.

8. Verify the front fog lamps illuminate.

• If the front fog lamps do not illuminate

1. Ignition OFF, remove the 3 A fused jumper wire, remove both E29 Fog Lamp - Front.
2. Test for infinite resistance between the control circuit terminal C1 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, all OK.

• Go to next step: If the front fog lamps illuminate

9. Ignition OFF, connect the X2 harness connector at the X50A Fuse Block - Underhood.

10. Disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.

NOTE: The test lamp in the following step will illuminate at LOW intensity.

This is normal circuit operation and does not indicate a circuit malfunction.

11. Verify a test lamp illuminates between the control circuit terminal 20 and ground.

• If the test lamp does not illuminate

1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
2. Test for infinite resistance between the control circuit terminal 20 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the X50A Fuse Block - Underhood.

• Go to next step: If the test lamp illuminates

12. Ignition OFF, connect a 3 A fused jumper between the control circuit terminal 20 and ground, ignition ON.

13. Verify both E29 Fog Lamp - Front illuminate.

• If the front fog lamps do not illuminate

1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood, ignition ON.
2. Test for less than 1 V between the control circuit terminal 20 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the X50A Fuse Block - Underhood.

• Go to next step: If the front fog lamps illuminate

14. Test or replace the K9 Body Control Module.

Front Fog Lamp Indicator Malfunction

1. Ignition ON.

2. Verify the front fog lamp indicator turns ON and OFF when commanding the Instrument Cluster All Indicators Test ON and OFF with a scan tool.

• If the front fog lamp indicator is always OFF or remains ON

Replace the P16 Instrument Cluster.

• Go to next step: If the front fog lamp indicator turns ON and OFF

3. Replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Headlamp Switch Replacement
• Front Fog Lamp Replacement
• Engine Wiring Harness Fuse Block Bracket Replacement
• Control Module References for BCM or instrument cluster replacement, programming, and setup

READ NEXT: