Service Information

Volt

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

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Ambient Light Sensor Signal	B2645 03	B2645 03	B2645 07	--
Ground	--	1	--	--
1. Daytime Running Light Malfunction DTC B2645 03 - Ambient Light Sensor Circuit Low Voltage DTC B2645 07 - Ambient Light Sensor Circuit High Voltage

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ambient Light Sensor Signal

B2645 03

B2645 07

Ground

1. Daytime Running Light Malfunction

DTC B2645 03 - Ambient Light Sensor Circuit Low Voltage

DTC B2645 07 - Ambient Light Sensor Circuit High Voltage

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 dipped beam headlamps ON.

Reference Information

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

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

If the reading is out of specified range, verify that DTC B2645 is not set. If the DTC is set, refer to DTC B2645 .

Circuit/System Testing

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

Vehicle in Service Mode 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.

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

Component Testing

Static Test

Vehicle in Service Mode, observe the scan tool Ambient Light Sensor parameter. The reading should be between 1.4-4.5 V and change with ambient light changes.
Test the B10B Ambient Light/Sunload Sensor by varying the ambient light while monitoring the sensors voltage output.
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, programming and setup