GDL Bulbs (2006-2013): Function: Headlights
If the knob is in the correct position in the light switch module (LSM) (3/111), the central electronic module (CEM) is instructed to light low beam.
The central electronic module (CEM) (4/56) powers the Bi-Xenon lamps directly via an output.
To switch to high beam, the left control stalk is pulled toward the steering wheel. A directly connected signal is sent from the steering wheel module (SWM) (3/254) to the central electronic module (CEM), which passes on the request to the "master" gas discharge lamp module (GDL) via LIN communication.
The "master" module passes on the request to the "slave" module via LIN communication. Both LIN control module regulate the actuator motor (solenoid), which controls the position of the cover so that high beam is obtained for the Bi-Xenon light.
The central electronic module (CEM) also transmits a CAN signal to the driver information module (DIM) (5/1) to light the indicator lamp for high beam.
There is a Limp Home function which ensures that low beam still works if there is a fault in the control area network (CAN). For Bi-Xenon lamps the beam is then set to the shortest range.