Central Electronic Module (CEM) (2006-2013): Design: Headlamps

The headlamps are operated via the light switch module (LSM). This is on the dashboard at the side of the steering wheel. The light switch module (LSM) is directly connected to the central electronic module (CEM). Low and high beam are operated by moving the left-hand control stalk towards the steering wheel.

Low beam is powered directly by the central electronic module (CEM). High beam is powered via a directly connected relay on the central electronic module (CEM). The level of the supply voltage to the low beam is regulated by the central electronic module (CEM). When the supply voltage is sufficient (in excess of 13 V), pulse width modulation is used to maintain the voltage level at 13.0 V +/- 0.2 V. This does not apply to cars with Bi-Xenon lamps.

Cars with Bi-Xenon lamps are powered directly via the central electronic module (CEM) without pulse width modulation.

In Bi-Xenon lamps, the reflector in the lamp housing is moved by an actuator motor when changing between high and low beam. The actuator motor is integrated in the lamp housing.

To detect problems with the low beam, the central electronic module (CEM) reads the power consumption of the circuit. If this falls below a certain threshold value a fault will be indicated. The general warning lamp lights in the driver information module (DIM) and a text message is displayed.

There are diagnostics for the high beam relay.

There are also diagnostics for the high and low beam function (actuator motor) for Bi-Xenon lamps.

Right and left-hand asymmetric lamps 

The right and left-hand asymmetric lamps are adjusted mechanically using a simple operation. A lever is accessible when the rear cover on the headlamp housing is opened.

Halogen 

A = left-hand asymmetric

B = right-hand asymmetric

Bi-Xenon 

A = left-hand asymmetric

B = right-hand asymmetric