Left Headlight Control Unit (LHCU) / Right Headlight Control Unit (RHCU)
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 Central electronic module (CEM) 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 Central electronic module (CEM).
If there is no communication with the Central electronic module (CEM) 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 (shortest beam length is used straight ahead).
The left headlight control unit (LHCU) and right headlight control unit (RHCU) can be diagnosed.
The control units are integrated in the headlamps. If a Left headlamp control unit (LHCU) or Right headlamp control unit (RHCU) becomes damaged, the entire headlamp must be replaced, for certain models.