Daytime Running Lamps (DRL) Inoperative

DAYTIME RUNNING LAMPS (DRL) INOPERATIVE




DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

CIRCUIT/SYSTEM DESCRIPTION
The ambient light sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 1.75-4.9 volts depending on outside lighting conditions. The body control module (BCM) provides a low reference ground and 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 high outside light 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.

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the ambient light sensor.
2. Install a 3-amp fused jumper between the ambient light sensor signal and low reference circuits.
3. Ignition ON, install a scan tool and display the Day/Night Status parameter in the BCM lighting data list. The scan tool should display Day.
- If the scan tool displays Night, repair the ambient light sensor low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
4. If all circuits test normal, replace the ambient light sensor.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

- Ambient Light Sensor Replacement
- Control Module References for BCM replacement, setup, and programming