Headlamp Leveling Motor
Headlamp Leveling Motor
Description
The headlamp leveling motor (2) is located on the rear outboard side of each front lamp unit housing (1) on vehicles equipped with the headlamp leveling system, which is available only in certain markets where it is required equipment. The motor is encased within a molded plastic housing and is secured by an integral wedge-type mounting boss to a keyed flange on the back of the front lamp unit housing. A rubber seal around the circumference of the mounting boss seals the motor to the lamp housing.
The outside of the motor housing features an integral molded connector on its rearward surface and a plastic pushrod with a ball formation on its free end extends from the motor mounting boss. Within the motor housing is a 12-volt Direct Current (DC) servo motor, an electronic controller board that includes the motor logic circuits, and an integral screw-drive transmission. The headlamp leveling motor is connected to the vehicle electrical system through a dedicated take out and connector of the front end module wire harness.
The headlamp leveling motor is serviced as a unit with the front lamp unit. The motor cannot be repaired and, if ineffective or damaged, the entire front lamp unit must be replaced.
Operation
The controller board and logic circuitry of the headlamp leveling motor controls motor operation based upon a voltage signal input received from the Totally Integrated Power Module (TIPM). On vehicles with halogen lighting and the manual headlamp leveling system, the TIPM uses electronic messages received over the Controller Area Network (CAN) data bus from the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) to determine the correct voltage signal to provide the leveling motor, while the EMIC uses electronic messages received over the Local Interface Network (LIN) data bus from the instrument panel switch pod to monitor the headlamp leveling switch selection.
On vehicles with High Intensity Discharge (HID) lighting and the automatic headlamp leveling system, the TIPM uses electronic messages received over the Controller Area Network (CAN) data bus from the Automatic Headlamp Leveling Module (AHLM) (also known as the High Intensity Discharge Transducer/HIDT) 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 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.
The hard wired circuits for the headlamp leveling motors may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the active electronic elements within the headlamp leveling motors or the electronic controls and communication between other modules and devices that provide some features of the headlamp leveling system. The most reliable, efficient, and accurate means to diagnose the headlamp leveling motor or the electronic controls and communication related to headlamp leveling system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.