System Overview: Control

Fig 1: Identifying Bi-Xenon Headlight Control System Diagram

Courtesy of VOLVO CARS CORPORATION

1.	Central electronic module (CEM)	4.	Motor, headlight levelling
2.	Rear electronic module (REM)	5.	Suspension module (SUM) (only vehicles with Four-C (Continuously Controlled Chassis Concept))
3.	Position sensors

An electric motor is controlled by the central electronic module (CEM) via a relay (standard high beam relay).

The motor drives a gear that moves the reflector along its guides.

A sensor connected to the motor detects the position of the reflector.

The motor electronics interpret the sensor information and generate a signal.
The signal is fed back to the central electronic module (CEM).

If the reflectors are in the wrong position for high beam, the are forced down into a so-called safety position;

the warning lamp (orange) in the driver information module (DIM) illuminates
an error message appears in the driver information module (DIM) display.

If high beam is activated with the light switch in position 0, high beam is only activated while the stalk is in the high beam position, so-called high beam flash. In order for high beam to remain on, the light switch must be in the "On" position.