Motor, Headlamp Leveling: Operation

The controller board and logic circuitry of the headlamp leveling motor controls motor operation based upon a voltage signal input received from the Body Control Module (BCM). On vehicles with High Intensity Discharge (HID) lighting and the automatic headlamp leveling system, the BCM uses electronic messages received over the Controller Area Network (CAN) data bus from the Automatic Headlamp Leveling Module (AHLM) to determine the correct voltage signal to provide the leveling motor.

The headlamp leveling motors have a path to ground at all times. The motors operate on battery voltage received through the headlamp low beam feed circuits so that the system will only operate when the headlamp low beams are turned ON. When the motor is energized it will extend or retract the motor pushrod through an integral screw-drive transmission. The ball on the end of the pushrod is snapped into a socket clip on the back of the reflector within the front lamp unit housing, which will cause the reflector to move as the pushrod is extended or retracted, changing the angle at which the light is projected from the headlamp.