Sprinter 2500 V6-3.0L DSL Turbo VIN 45 (2007)
Headlamp Alignment Actuator: Description and Operation
Headlamp Leveling Module
Description
DESCRIPTION
An Automatic Headlamp Leveling Module (AHLM) (1) (also known as the Adaptive Lighting, Headlamp Range Adjustment/HRA or LWR module) is
standard equipment with the optional bi-xenon (also known as High Intensity Discharge/HID) headlamps. The AHLM is located in the passenger
compartment. This unit is designed to work in conjunction with the front and rear axle sensors and the headlamp leveling motors to provide automatic
headlamp beam adjustment to compensate for changes in vehicle height cased by changes in vehicle loading, acceleration or deceleration.
The AHLM has two integral mounts (3) that are secured by two nuts to two weld studs on the right cowl side inner panel just forward of the right front
door opening. The module is concealed beneath the cowl side inner trim panel. Concealed within the molded plastic housing is the circuitry of the
module, which includes a microprocessor. The module is connected through an integral connector receptacle (2) to the vehicle electrical system by a take
out and connector of the vehicle wire harness.
The AHLM cannot be adjusted or repaired and, if ineffective or damaged, it must be replaced.
Operation
OPERATION
The microprocessor in the Automatic Headlamp Leveling Module (AHLM) (1) (also known as the Adaptive Lighting, Headlamp Range
Adjustment/HRA or LWR module) contains the logic circuits and controls all of the features of the automatic headlamp leveling system. The AHLM
uses On-Board Diagnostics (OBD) and can communicate with other modules in the vehicle as well as with a diagnostic scan tool using the Controller
Area Network (CAN) data bus. This method of communication is used by the AHLM to communicate with the ElectroMechanical Instrument Cluster
(EMIC) (also known as the Cab Compartment Node/CCN or KOMBI), the Electronic Ignition Switch (EIS) (also known as the Electronic Ignition
Switch/Central GateWay/EIS/CGW or EZS) and with the Controller Antilock Brake (CAB) (also known as the Antilock Brake System/ABS or
Electronic Stability Program/ESP controller).
The AHLM microprocessor continuously monitors inputs from the EMIC, the EIS and the CAB. The AHLM then energizes or de-energizes the front and
rear axle sensors which monitor the vehicle height, and the headlamp leveling motors which adjust the headlamp reflectors. When the axle sensors are
energized, the AHLM monitors and evaluates the Pulse Width Modulated (PWM) signals from the sensors and actuates the headlamp leveling motors on
each front lamp unit as appropriate. The AHLM also monitors all of the system circuits, then sets active and stored Diagnostic Trouble Codes (DTC) for
any monitored system faults it detects.
The AHLM receives battery voltage on a fused ignition switch output (ON) circuit through a fuse in the fuse and relay block (also known as the SRB),
and is grounded at all times through a hard wired remote ground point. These connections allow the AHLM to operate only when the ignition switch is in
the ON position.
The hard wired circuits of the AHLM 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 AHLM or the electronic controls or communication between
modules and other devices that provide some features of the automatic headlamp leveling system. The most reliable, efficient, and accurate means to
diagnose the AHLM or the electronic controls and communication related to automatic headlamp leveling system operation requires the use of a
diagnostic scan tool. Refer to the appropriate diagnostic information.