Headlamp range adjustment (HRA) headlamp function - GF82.10-P-1001GX

MODEL 164.1/8 with CODE (615) Bi-xenon headlamp unit with integrated curve illumination up to Model Year 2008 

Task 

The headlamp range adjustment is prescribed by law for vehicles with xenon headlamps to prevent them dazzling oncoming traffic.

The headlamp range adjustment automatically keeps the incline angle of the driving lights within the legal limits when the vehicle level changes, which is caused either by loads in the vehicle or by dynamic changes (e.g. acceleration, deceleration).

Function requirements 

• Circuit 61 ON

Function (up to 8.7.07) 

For vehicles without code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS) the data from the front right level sensor (B22/9) and the rear right level sensor (B22/10) are read in directly by the headlamp range adjustment control unit (N71).

For vehicles with code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS) the headlamp range adjustment control unit receives the level values from the AIRmatic control unit (N51) via the Controller Area Network bus class C (engine compartment) (CAN-C).

The headlamp range adjustment control unit forwards the evaluated data over a serial interface to the HRA [LWR] power module (E1n3) and to the HRA [LWR] power module (E2n3). The HRA [LWR] power module on the front left lamp unit (E1) actuates the left headlamp range adjustment motor (E1m1), the HRA [LWR] power module on the front right lamp unit (E2) actuates the right headlamp range adjustment motor (E2m1). The headlamp range adjustment motors signal their respective positions to the HRA [LWR] power modules via internal potentiometers.

As of 9.7.07 the headlamp range adjustment is controlled by the xenon headlamp control unit (E1n1) and by the xenon headlamp control unit (E2n1).

Function (as of 9.7.07) 

To correct the range of the front left lamp unit and the front right lamp unit, the xenon headlamp control units must

• calculate the body pitch angle from the positions of the axes
• correct the angle of the projection mode as a function of the body pitch angle
• evaluate the vehicle speed for the operating mode switch (static mode, dynamic mode)

The information regarding the axis positions for vehicles with code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS) is sent to the xenon headlamp control units by the AIRmatic control unit via CAN-C.

The information regarding the axis positions for vehicles without code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS) is sent by the front right level sensor and by the rear right level sensor directly to the xenon headlamp control unit for the front left lamp unit which relays these values over CAN-C to the xenon headlamp control unit for the front right lamp unit.

The information regarding the vehicle speed is sent to the xenon headlamp control units by the ESP control unit (N47-5) via CAN-C.

The xenon headlamp control units actuate the headlamp range adjustment motors accordingly in order to correct the range.

Treatment of fault 

With

• implausible messages or failure of CAN-C
• missing level values from the AIRmatic control unit (for code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS))
• defect in the headlamp range adjustment control unit (up to 8.7.07)
• defect in the xenon headlamp control units (as of 9.7.07)
• a defective level sensor (without code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS))
• a communication error between the HRA [LWR] power modules and the headlamp range adjustment control unit (up to 8.7.07)

the headlamp range adjustment motors move into the error position. If just one headlamp range adjustment motor is defective, it is disabled.

Up to 8.7.07:

Faults detected by the HRA [LWR] power modules are sent over a serial interface to the headlamp range adjustment control unit where they are stored in the fault memory and can be read out via diagnosis.

As of 9.7.07

All the headlamp range adjustment components are monitored constantly by the xenon headlamp control units. Faults that are detected are stored in the fault memory of the corresponding xenon headlamp control unit.

	Xenon light control unit, component description	E1n1, E2n1 As of 9.7.07	GF82.10-P-2119GZ
	Component description of headlamp range adjustment power module	E1n3, E2n3 up to 8.7.07	GF82.10-P-2117GZ
	ESP control unit, component description	N47-5	GF42.45-P-5118GZ
	AIRmatic with ADS control unit, component description	N51 For code (489) AIRmatic (air suspension with level adjustment and adaptive damping system ADS)	GF32.22-P-5108GZ
	Component description of headlamp range adjustment control unit	N71 up to 8.7.07	GF82.10-P-2112GZ