The ambient light sensor is used to monitor outside lighting conditions. The ambient light 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 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.

Ignition ON

B2645 03

The BCM detects a voltage below threshold on the signal circuit.

B2645 07

The BCM detects a voltage above threshold on the signal circuit.

The condition for setting the DTC is not longer present.

The condition for setting the DTC is not longer present.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

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.

1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor.
2. Test for less than 5 Ω between the low reference circuit harness connector terminal 6 and ground.

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

3. Connect the harness connector at the B10B Ambient Light/Sunload Sensor.
4. Disconnect the X2 harness connector at the K9 Body Control Module (BCM).
5. Ignition ON, test for 4.8-5.2 V between the signal circuit X2 harness connector terminal 10 and ground.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the B10B Ambient Light/Sunload Sensor.

⇒	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 B10B Ambient Light/Sunload Sensor.

6. If all circuits test normal, test the K9 Body Control Module (BCM).

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.

Perform the Diagnostic Repair VerificationDiagnostic Repair Verification after completing the diagnostic procedure.