Daytime Running Lamps Malfunction

Daytime Running Lamps Malfunction

Diagnostic Instructions

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



Diagnostic Fault Information






Circuit/System Description

The ambient light sensor is a light sensitive transistor that varies the voltage signal to the body control module (BCM) based on outside lighting conditions. When the ambient light sensor indicates daytime conditions with engine running, the BCM, will then apply battery voltage through the front turn signal lamp supply voltage circuits illuminating the left and right front turn lamps. Any function or condition that turns the headlamps ON will cancel DRL operation.


Reference Information
Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Programming and Relearning (Programming and Relearning) for Scan Tool Information


Circuit/System Verification

1. Ignition ON, verify that the left and right front turn signals operate. If not refer to Turn Signal Lamps and/or Indicators Malfunction (Turn Signal Lamps and/or Indicators Malfunction) .
2. Ignition ON, observe the scan tool Ambient Light Status parameter while carefully supplying sufficient light to simulate daylight conditions to the ambient light sensor for more than 30 seconds. The reading should be Day.
3. Engine running in daylight conditions with the headlamp switch in the Auto position, the front turn signal lamps should illuminate as daytime running lamps.



Circuit/System Testing

1. Carefully supplying sufficient light to simulate daylight conditions to the ambient light sensor for more than 30 seconds.
2. Ignition ON, observe the scan tool Ambient Light Status parameter. The reading should be Day.

• If not the specified value, replace the ambient light sensor.
• If the specified value, replace the BCM.




Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Ambient Light Sensor Replacement (Service and Repair)
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup, and programming