Battery positive voltage is applied to the headlamp control module at all times and when the ignition switch is in the RUN and CRANK positions. The headlamp control module has an operational voltage range of about 10.5-16 volts and is only fully functional when the ignition switch is in the RUN position. The voltage input from the ignition switch wakes the headlamp control module microprocessor. The headlamp control module receives serial data messages via serial data from the engine control module (ECM), transmission control module (TCM), electronic brake control module (EBCM), and body control module (BCM) with regards to power mode, speed, steering angle, transmission gear selection, and headlamp switch status. The headlamp control module calculates the headlamp angle and sends commands to the left and right adaptive forward lighting system (AFL) headlamp actuators. The headlamp actuators drive the headlamps to the position commanded by the headlamp control module. The headlamp control module monitors the headlamp actuator motor control circuits for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a DTC will be stored in memory and the driver will be notified with a message displayed over the driver information center (DIC) located on the instrument panel cluster (IPC).

Diagnose any faults to the vehicle stability enhancement system (VSES) which contains the steering wheel position sensor before proceeding with this diagnostic procedure. A fault within the steering wheel position sensor will cause the adaptive forward lighting system to be inoperative.

Schematic Reference

Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, with a scan tool, command the Headlamp Motor Test ON while observing both headlamps. Both headlamps should operate to the Left and Right positions when commanded.

1. Ignition OFF, disconnect the harness connector at the appropriate headlamp actuator.
2. Ignition OFF, test for less than 10 ohms between the control circuit terminal 1 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

3. Ignition OFF, test for less than 10 ohms between the control circuit terminal 2 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

4. Ignition OFF, test for less than 10 ohms between the control circuit terminal 3 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

5. Ignition OFF, test for less than 10 ohms between the control circuit terminal 4 and ground.

⇒	If greater than the specified range, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the headlamp control module.

6. Connect a test lamp between control circuit terminal 1 and control circuit terminal 3.
7. Command the Headlamp Motor Test ON with a scan tool. The test lamp should turn ON when commanding the Left and Right states.

⇒	If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the headlamp control module.

8. Connect a test lamp between control circuit terminal 2 and control circuit terminal 4.
9. Command the Headlamp Motor Test ON with a scan tool. The test lamp should turn ON when commanding the Left and Right states.

⇒	If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the headlamp control module.

10. If all circuits test normal, replace the appropriate headlamp assembly.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.