The ambient light sensor is used to monitor outside lighting conditions. The body control module (BCM) provides a 5-volt reference signal to the ambient light sensor. The sensor is a variable resistor, it's resistance changes as outside lighting conditions change. With the headlamp switch in the AUTO position, the BCM monitors the sensor signal circuit to determine if the outside lighting conditions are correct for either daytime running lamps (DRL) or headlamp operation. In daylight conditions, the BCM will command the DRLs ON. In low light conditions, the BCM will command the headlamps ON.

The DTC will set when the BCM detects the ambient light sensor signal voltage is below 0.2 volts or above 4.9 volts.

The BCM defaults to low light status and commands the headlamps ON.

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

1. Ignition OFF, disconnect the harness connector at the ambient light sensor (RPO C67) or sunload sensor assembly (RPO CJ2).
2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal B (C67) or C (CJ2) and ground.

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

3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 volts.

⇒	If less than the specified range, test the signal circuit terminal A (C67) or D (CJ2) for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal A (C67) or D (CJ2) and the low reference circuit terminal ground. Verify the scan tool Ambient Light Sensor parameter is less than 0.2 volts.

⇒	If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the ambient light sensor (C67) or sunload sensor assembly (CJ2).

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.