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/System Description
Daytime Running Lamps (T4A)
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 V depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor which is permanently grounded. The BCM 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 when the headlamp switch is in the AUTO position. In daylight conditions the BCM will command the low beam headlamps ON by applying a pulse width modulated (PWM) voltage to the left and right low beam headlamp control circuits illuminating the low beam headlamps. Any function or condition that turns on the headlamps will cancel DRL operation.
Daytime Running Lamps (T4F)
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 V depending on outside lighting conditions. The body control module (BCM) provides a 5 V reference signal to the ambient light sensor which is permanently grounded. The BCM 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 when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will command the DRLs ON by applying a pulse width modulated (PWM) voltage to the left and right DRL control circuits illuminating the DRLs. Any function or condition that turns on the headlamps will cancel DRL operation.
Reference Information
Schematic Reference
Headlights Schematics (Headlights Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
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
Daytime Running Lamps (T4A)
1. Ignition ON, headlamps OFF, command the Low Beam Headlamps ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when changing between the commanded states.
• If the low beam headlamps do not change between the commanded states, refer to Headlamps Malfunction (Headlamps Malfunction).
2. Observe the scan tool Ambient Light Status parameter while supplying sufficient light to simulate daylight conditions to the ambient light sensor. After 30 seconds, the parameter should be Daylight.
• If not the specified value, refer to the Ambient Light Sensor Malfunction.
Daytime Running Lamps (T4F)
1. Ignition ON, headlamps OFF, command the Low Beam Headlamps ON and OFF with a scan tool. The low beam headlamps should turn ON and OFF when changing between the commanded states.
• If the low beam headlamps do not change between the commanded states, refer to Headlamps Malfunction (Headlamps Malfunction).
2. Headlamps OFF, command the Left or Right Dedicated Daytime Running Lamp Command ON and OFF with a scan tool. The daytime running lights should turn ON and OFF when changing between the commanded states.
• If the daytime running lamps do not change between the commanded states, refer to Daytime Running Lamp Malfunction.
3. Observe the scan tool Ambient Light Status parameter while supplying sufficient light to simulate daylight conditions to the ambient light sensor. After 30 seconds, the parameter should be Day.
• If not the specified value, refer to the Ambient Light Sensor Malfunction.
Circuit/System Testing
Ambient Light Sensor Malfunction
1. Ignition OFF, disconnect the harness connector at the B10 ambient light sensor.
2. Ignition OFF, test for less than 5 ohm between the ground circuit terminal 6 and ground.
• If greater than the specific 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 5 for a short to ground. If the circuit tests normal, replace the K9 BCM.
4. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the ground circuit terminal 6. Verify the scan tool Ambient Light Sensor parameter is less than 0.196 V.
• If greater than the specified range, test the signal circuit for a short to voltage an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, replace the B10 ambient light sensor.
Daytime Running Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate E4 daytime running lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5.0 ohm between the ground circuit terminal 2 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the signal circuit terminal 1 and ground.
4. Command the Dedicated Daytime Running Lamp Command 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 K9 BCM.
• 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 K9 BCM.
5. If all circuits test normal, replace the E4 daytime running lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Automatic Control Ambient Light Sensor Replacement (Service and Repair)
* Daytime Running Lamp Replacement (Daytime Running Lamp Replacement)
* Daytime Running Lamp Bulb Replacement (Daytime Running Lamp Bulb Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming