Left Headlamp Control Unit (LHCU)/Right Headlamp Control Unit (RHCU) (Vehicles With Active Headlamps Only)
A control module is mounted beneath each lamp housing on vehicles with active headlamps.
The left headlamp control unit (LHCU) and right headlamp control unit (RHCU) handle headlamp levelling and active control of the light beam. Active control means that the light beam is turned out to the left or right. The light beam is turned out at varying degrees and rates depending on vehicle speed and steering angle.
Information is transferred between the left headlamp control unit (LHCU), right headlamp control unit (RHCU) and headlamp control module (HCM) via serial communication.
The lamp housing contains a sensor that indicates whether the light beam has been turned out to the right or left. The left headlight control unit (LHCU) and right headlight control unit (RHCU) send this information to the headlight control module (HCM).
If there is no communication with the headlamp control module (HCM) or there is a fault in the left headlamp control unit (LHCU) and/or right headlamp control unit (RHCU), headlamp levelling and active control are disabled. The light beam then assumes its "limp-home" position.
The left headlight control unit (LHCU) and right headlight control unit (RHCU) can be diagnosed.