The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary depending on outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lights (DRL) or automatic lamp control (ALC) when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON. In low light conditions, when the headlamps switch is in AUTO position, the BCM will command the low beam headlamps ON.

Battery voltage must be between 9-16 volts.

B2645 03

The DTC will set when the BCM detects voltage is below 0.196 volt in the ambient light sensor signal circuit.

B2645 07

The DTC will set when the BCM detects voltage is above 4.9 volts in the ambient light sensor signal circuit or if the ambient light sensor ground circuit is open.

When DTC B2645 03 or B2645 07 is present, the ALC will default to ON.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Lighting Systems Connector End Views

Electrical Information Reference

Scan Tool Reference

1. Ignition OFF, disconnect the ambient light sensor.
2. Ignition ON, monitor the Ambient Light Sensor parameter in the BCM data list with a scan tool.

⇒	If the scan tool parameter is less than 0.2 volt, test for a short to ground in the ambient light sensor signal circuit. If a short to ground is not found, replace the BCM.

⇒	If the scan tool parameter is greater than 4.9 volts, test for an open or short to voltage in the ambient light sensor signal circuit or an open in the ambient light sensor ground circuit. If any of those conditions are not found, replace the ambient light sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.