Daytime Running Lamps Malfunction
Daytime Running Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit 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, the body control module (BCM) grounds the DRL relay control circuit energizing the DRL relay. With the DRL relay energized, the switch contacts close and voltage is applied to the DRL 1 and DRL 2 fuses to the left and right low beam headlamps. Any function or condition that turns on the headlamps will cancel DRL operation.
Reference Information
Schematic Reference
Headlights/Daytime Running Lights (DRL) Schematics (Headlights/Daytime Running Lights (DRL) Schematics)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Exterior Lighting Systems Description and Operation (Exterior Lighting Systems)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, with a scan tool command the Low Beams ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states.
• If the low beam headlamps do not turn ON and OFF when commanded, refer to Headlamps Malfunction (Headlamps Malfunction).
2. Ignition ON, park brake released, verify with a scan tool the Park Brake Switch parameter displays Released.
• If not the specified value, refer to Brake Warning Indicator Malfunction (Brake Warning Indicator Malfunction).
3. Ignition ON, with a scan tool command the DRL ON and OFF. The low beam headlamps should turn ON and OFF when changing between the commanded states.
• If the low beam headlamps turn ON and OFF when commanded, refer to Ambient Light Sensor Malfunction.
• If the low beam headlamps do not turn ON and OFF when commanded, refer to Daytime Running Lamps Malfunction.
Circuit/System Testing
Ambient Light Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the ambient light sensor.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool Ambient Light Sensor parameter is greater than 4.65 V.
• If less than the specified range, test the signal circuit terminal A or a short to ground. If the circuit tests normal, replace the BCM
4. Install a 3 A fused jumper wire between the signal circuit terminal A and ground. Verify the scan tool Ambient Light Sensor parameter is less than 1.96 V.
• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the ambient light sensor.
Daytime Running Lamps Malfunction
1. Ignition OFF, disconnect the X4 harness connector at the underhood fuse block.
2. Connect a test lamp between B+ and the control circuit terminal H2.
3. 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.
4. Ignition OFF, connect the X4 harness connector at the underhood fuse block.
5. Disconnect the X3 harness connector at the underhood fuse block.
6. Connect a test lamp between the control circuit terminal B2 and ground.
7. 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 voltage. If the circuit tests normal, replace the underhood fuse block.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the underhood fuse block.
8. If all circuits test normal, replace the underhood fuse block.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Accessory Wiring Junction Block Replacement (Accessory Wiring Junction Block Replacement)
* Daytime Running Lamp (DRL) Ambient Light Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming