Daytime Running Lamps (DRL) Inoperative

DAYTIME RUNNING LAMPS (DRL) INOPERATIVE

DIAGNOSTIC INSTRUCTIONS
- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.




DIAGNOSTIC FAULT INFORMATION

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 0.2 and 4.9 volts depending on outside lighting conditions. The HVAC control module provides a low reference ground and a 5-volt reference signals to the ambient light sensor. The HVAC control module 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. The HVAC control module sends a signal to the body control module (BCM) via class 2 serial data commanding the BCM to turn the front turn signal lamps on steady (non-flashing). Any function or condition that turns on the headlamps will cancel the DRL operation. With the turn signal/multifunction switch in the OFF position, the turn signal lamps will either be turned ON or OFF after a 30-second delay, depending on whether daylight or low light conditions are sensed by the ambient light sensor.

DIAGNOSTIC AIDS

IMPORTANT: This diagnostic procedure assumes that the turn signal lamps are operating within specifications. If the turns signal lamps are inoperative, diagnose the turn signal malfunction before proceeding with the following diagnostic. Refer to Turn Signal Lamps and/or Indicators Malfunction. Turn Signal Lamps and/or Indicators Malfunction

CIRCUIT/SYSTEM VERIFICATION
Ignition ON, verify with a scan tool the park brake switch parameter displays RELEASED.
- If not the specified value, refer to Symptoms - Hydraulic Brakes. Symptoms - Hydraulic Brakes

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the harness connector at the sunload sensor assembly.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal C and ground.
- If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
3. Install a 3A fused jumper wire between the signal circuit terminal D and the low reference circuit terminal C. Verify the scan tool Day/Night status parameter is DAY.
- If the scan tool displays NIGHT, test the signal 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 sunload sensor assembly.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

- Sun Load Sensor Replacement
- Control Module References for BCM or HVAC control module replacement, setup, and programming. Programming and Relearning