Daytime Running Lamps Malfunction

Daytime Running Lamps Malfunction

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy 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 body control module (BCM) grounds the DRL relay control circuit, energizing the DRL relay. With the DRL relay energized, voltage is applied through the relay switch contacts, the DRL Resistor , and the DRL fuse to the left and right low beam headlamps. Any function or condition that turns the headlamps ON will cancel DRL operation.


Reference Information
Schematic Reference

Interior Lights Schematics (Interior Lights 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

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

Ignition ON, the headlamp switch in the headlamp ON position. Observes the headlamps, the headlamps should be ON.


Circuit/System Testing

1. Ignition OFF, disconnect the DRL relay.
2. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.

• If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Command the DRL ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

6. Connect a 10A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the DRLs do not illuminate.

• If the DRLs illuminate, test or replace the DRL relay.

7. With the jumper wire still connected, disconnect the DRL resistor.
8. Verify that a test lamp illuminates at one of the terminals of the DRL resistor.

• If the test lamp does not illuminate, test for a short to ground or an open/high resistance in the DRL control circuit between the underhood fuse block and the I/P fuse block.

9. Connect a 10A fused jumper wire between both terminals of the DRL resistor. The DRLs should illuminate.

• If the DRLs do not illuminate, replace the underhood fuse block.




Repair Instructions

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

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Underhood Electrical Center or Junction Block Replacement (Underhood Electrical Center or Junction Block Replacement)
* Instrument Panel Wiring Harness Junction Block Replacement (Instrument Panel Wiring Harness Junction Block Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming