Daytime Running Lamps Malfunction
Daytime Running Lamps Malfunction
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
Conditions for Running the DTC
The body control module (BCM) receives a signal from the ambient light sensor indicating a low or high ambient outside light level. Under daylight conditions the BCM grounds the DRL relay control circuit energizing the DRL relay. The now closed relay supplies voltage to the DRLs. Any time the headlamps are illuminated the DRL will not illuminate.
Circuit/System Verification
Supply sufficient light to simulate daylight conditions to the ambient light sensor. Ignition ON, engine running, and the gear selector in drive. The DRLs should illuminate.
Circuit/System Testing
1. Supply sufficient light to simulate daylight conditions to the ambient light sensor.
2. Ignition ON, headlamp switch in the AUTO position.
3. Observe the headlamps. The headlamps should not be illuminated.
^ If the headlamps are illuminated, replace the ambient light sensor.
4. Ignition OFF, disconnect the DRL relay.
5. Ignition ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal 87 and ground.
^ If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.
6. Verify that a test lamp illuminates between the relay coil B+ circuit terminal 86 and ground.
^ If the test lamp does not illuminate, test the relay coil B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the DRL relay.
7. Verify that a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.
^ If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high resistance.
8. Connect a test lamp between the relay coil B+ circuit terminal 86 and the relay coil control circuit terminal 85.
9. 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 relay coil control circuit for a short to ground. If the circuit tests normal, replace the BCM.
^ If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
10. 8. Connect a 10A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87.
11. Disconnect the harness connector at one of the DRLs.
12. Verify that a test lamp illuminates between the DRL voltage supply circuit listed below and ground:
* RPO W49 - terminal 3
* RPO WDA - terminal 2
* RPO Z88 - terminal 1
^ If the test lamp does not illuminate, test the voltage supply circuit for a short to ground or an open/high resistance.
13. Verify that a test lamp illuminates between the DRL ground circuit listed below and B+:
* RPO W49/WDA - terminal 1
* RPO Z88 - terminal 3
^ If the test lamp does not illuminate, test the ground circuit for a open/high resistance.
14. If all circuits test normal, test or replace the DRL relay.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* Daytime Running Lamp (DRL) Ambient Light Sensor Replacement (With UV6) Daytime Running Lamp (DRL) Ambient Light Sensor Replacement (Without UV6)