Buick Regal: Automatic Light 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 Light Malfunction

Circuit/System Description

The ambient light/sunload sensor is used to monitor outside lighting conditions. The ambient light/sunload sensor provides a voltage signal that will vary between 1.4 - 4.5 V depending on outside lighting conditions. The body control module (BCM) monitors the ambient light/sunload sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the daytime running lights ON. During low light conditions the BCM will command the low beam headlamps ON.

Reference Information

Schematic Reference

Headlights/Daytime Running Lights (DRL) 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

Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4 - 4.5 V and change with ambient light changes.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor.

2. Test for less than 5 Ω between ground circuit harness connector terminal 6 and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8 - 5.2 V between B10B Ambient Light/Sunload Sensor signal circuit harness connector terminal 5 and ground.

• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module.

4. If all circuits test normal, replace the B10B Ambient Light/Sunload Sensor.

Component Testing

Static Test

1. Ignition ON, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4 - 4.5 V and change with ambient light changes.

2. Test the B10B Ambient Light/Sunload Sensor by varying the ambient light while monitoring the sensors voltage output.

3. Verify that the voltage output is within the range of the specification.

• If not within the specified range, replace the B10B Ambient Light/Sunload Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

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