Buick Regal: Daytime Running 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. Daytime Running Lamps Malfunction

Circuit/System Description

The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 V depending on outside lighting conditions.

The body control module (BCM) provides a 5 V reference signal to the ambient light sensor and the HVAC control module provides a low reference ground. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the daytime running lamps ON. During low light conditions the BCM will command the low beam headlamps ON. Any function or condition that turns on the headlamps will cancel daytime running lamps operation. With the vehicle in park, the BCM commands the park lamps on which utilizes the same lamps as the daytime running lamps. Once the vehicle is in gear, the BCM then commands the daytime running lamps on with a separate circuit from the park lamps.

Reference Information

Schematic Reference

• Headlights/Daytime Running Lights (DRL) Wiring Schematics
• Body Control System 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.

2. Verify the left daytime running lamp turns ON & OFF when commanding the Left Dedicated Daytime Running Lamp ON and OFF with a scan tool.

• If the left daytime running lamp does not turn ON and OFF

Refer to Circuit/System Testing - Daytime Running Lamps Malfunction.

• Go to next step: If the left daytime running lamp turns ON and OFF

3. Verify the right daytime running lamp turns ON & OFF when commanding the Right Dedicated Daytime Running Lamp ON and OFF with a scan tool.

• If the right daytime running lamp does not turn ON and OFF

Refer to Circuit/System Testing - Daytime Running Lamps Malfunction.

• Go to next step: If the right daytime running lamp turns ON and OFF

4. Refer to Circuit/System Testing - Ambient Light Sensor Malfunction.

Circuit/System Testing

Daytime Running Lamps Malfunction

1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E13 Headlamp Assembly. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.

• Terminal 1 (with T4A)
• Terminal 2 (with T4L)
• 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 9 and ground, ignition ON.

4. Verify the test lamp turns ON and OFF when commanding the appropriate Dedicated Daytime Running Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
   • X5 - left daytime running lamp
   • X7 - right daytime running lamp
2. Test for infinite resistance between the control circuit terminal 9 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 appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
   • X5 - left daytime running lamp
   • X7 - right daytime running lamp
2. Test for less than 1 V between the control circuit terminal 9 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
3. Test or replace the daytime running lamp.

Ambient Light Sensor Malfunction

1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, open and close drivers door, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor. It may take up to 2 min for all vehicle systems to power down.

2. Test for less than 15 Ω between the low reference circuit terminal 6 and ground.

• If 15 Ω or greater

1. Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K33 HVAC Control Module.

• Go to next step: If less than 15 Ω

3. Ignition ON.

4. Verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V.

• If 4.65 V or less

1. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the signal circuit terminal 3 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 greater than 4.65 V

5. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 6.

6. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.

• If 0.196 V or greater

1. Ignition OFF, disconnect the X2 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 3 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 less than 0.196 V

7. Test or replace the B10B Ambient Light/Sunload Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Sun Load Temperature and Headlamp Automatic Control Ambient Light Sensor Replacement
• Headlamp LED Driver Module Replacement
• Control Module References for BCM or HVAC Control Module replacement, programming, and setup

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