Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Master Electrical Component List

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

1. Release the park brake.
2. Turn ON the ignition, with the engine OFF.
3. Verify the twilight sentinel option is turned ON in the DIC.
4. Cover the ambient light sensor with a dark cloth.

Do the headlamps turn ON?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

1. Install a scan tool.
2. Access the Special Functions menu.
3. Select the Twilight Sentinel Reprogramming.
4. After the reprogramming is completed, cover the ambient light sensor with a dark cloth.

Do the headlamps turn ON?

Go to Step 11

Go to Step 4

1. Remove the ALC HDLP relay.
2. Using a test lamp, probe between the ALC HDLP battery positive voltage supply circuit and the ALC HDLP relay control circuit.
3. Turn ON the ignition switch, with the engine OFF.
4. Cover the ambient light sensor with a dark cloth.

Does the test lamp illuminate?

Go to Step 5

Go to Step 7

1. Turn OFF the ignition.
2. Install a fused jumper between battery positive voltage and the headlamp switch signal headlamps ON circuit.
3. Turn ON the ignition switch, with the engine OFF.

Do the headlamps turn ON?

Go to Step 9

Go to Step 8

Test the ALC HDLP relay control circuit for a open, short to ground or a short to battery positive voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

Inspect the ALC HDLP relay control circuit for a poor connection or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

Repair a poor connection or an open in the headlamp switch signal headlamps ON circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

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Important: Perform the setup procedure for the body control module. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System.

Replace the body control module. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 11

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Replace the ALC headlamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 11

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4