The daytime running lamps (DRL) operate based on an input from the ambient light sensor. When the sensor indicates daylight conditions and the exterior lamps are not required to be on, the BCM will activate only the low beam headlamps as the DRLs. The DRLs will operate with the ignition ON, the parking brake released, and the headlamp switch in the OFF or AUTO position.

Schematic Reference

Headlights/Daytime Running Lights (DRL) 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. Verify the headlamp switch is in the AUTO position and the park brake is released.
2. Ignition ON, verify DTC B2645 is not set.

⇒	If DTC B2645 is set, refer to DTC B2645 .

3. Verify the scan tool BCM Park Lamp Switch parameter is Off.

⇒	If not the specified value, refer to Park, License, and/or Tail Lamps Malfunction .

4. Verify the following scan tool BCM parameters are Off.

•	Low Beam Switch

•	High Beam Switch

•	Flash to Pass Switch

⇒	If any of the parameters are not the specified value, refer to Headlamps Malfunction .

5. Verify the scan tool BCM Headlamp Off Switch parameter is Inactive.

⇒	If not the specified value, refer to Headlamps Malfunction .

6. Verify the scan tool BCM Park Brake Switch parameter is Released.

⇒	If not the specified value, refer to Brake Warning Indicator Malfunction .

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.