Buick Regal: Rear 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. Rear Fog Lamps Malfunction
2. Rear Fog Lamp Switch Malfunction

Circuit/System Description

The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch.

The body control module (BCM) responds to the rear fog lamp request by applying voltage to the rear fog lamps control circuit which illuminates the rear fog lamps.

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

Circuit/System Verification

1. Ignition ON, park lamps ON.

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

• If the parameter does not change

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

• Go to next step: If the parameter changes

3. Verify the rear fog lamps turn ON and OFF when commanding the Rear Fog Lamp(s) Relay ON and OFF with a scan tool.

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

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

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

4. Verify the rear fog lamp indicator on the headlamp switch turns ON and OFF while commanding the rear fog lamp ON and OFF with the rear fog lamp switch.

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

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

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

5. All OK.

Circuit/System Testing

Rear 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 Rear Fog Lamps Switch parameter is Inactive.

• If not Inactive

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 6 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 6 and ground.

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

• If not Active

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 6 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.
   1. If 2 Ω or greater, repair the open/high resistance in the circuit.
   2. 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.

Rear Fog Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E58 Rear Compartment Lid Tail Lamp Assembly. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 5 Ω between the ground circuit terminal 4 and ground.

• If 5 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 5 Ω

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

4. Verify the test lamp turns ON and OFF when commanding the Rear Fog Lamp(s) Relay ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit 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 K9 Body Control Module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the X6 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp turns ON and OFF

5. Test or replace the appropriate E58 Rear Compartment Lid Tail Lamp Assembly.

Rear Fog Lamp Indicator Malfunction

1. Ignition ON.

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

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

Replace the P16 Instrument Cluster.

• Go to next step: If the rear 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
• Tail Lamp Replacement (5-Door Hatchback 68) Tail Lamp Replacement (5-Door Wagon 35)
• Control Module References for BCM or Instrument Cluster replacement, programming, and setup

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