Part 2

63 03 03 (047)
Adaptive headlights
E46/2, E46/C, E53, E83


Activation of stepper motor controllers
The control unit�for�adaptive�headlights (AHL control unit or light module) sends the stepper motor controllers (SMC) the nominal values for the positioner modules (position of positioner modules and speed of movement).
The control unit for adaptive headlights calculates the nominal values using the following signals:
- Vehicle road speed
- Steering angle (at speeds up to 50 km/h, dependent on encoding)
- Yaw rate (50 km/h upwards, see "Steering-angle sensor and DSC sensor" above)



Speed-dependent analysis of signals
The adaptive headlights are controlled by the following signals depending on the road speed: signals from the steering angle sensor or signals from yaw-rate sensor (in the DSC sensor). The encoding (at the end of the production line) determines the priority assigned to sensor signals above which speed threshold (see above).



Adjustment of headlight horizontal aim
The stepper motor controllers move the headlights to the right or left when the vehicle corners.
Horizontal range of movement of headlights:
- Inwards, i.e. towards center of vehicle: up to max. 8°
> E46/2, E46/C, E83: 7°
> E53: 8°
- Outwards: up to max. 15°
Example: Right-hand bend:
The right-hand headlight turns by up to 15° (the right-hand headlight is the "inside" headlight on a right-hand bend).
It therefore swivels outwards away from the vehicle center.
The left-hand headlight swivels through a maximum of 8° (the left-hand headlight swivels towards the vehicle center, i.e. inwards).
The headlight on the outside of the bend reaches its end position at the same time as the headlight on the inside of the bend, ensuring that the road is evenly illuminated.
On a right-hand bend, the left-hand headlight is on the outside of the bend. The right-hand headlight is on the inside of the bend.



Deactivation of adaptive headlights function under extreme handling conditions
If the vehicle drifts, skids and loses sideways grip, the adaptive headlights function is deactivated as follows:
- The headlights are returned to the straight-ahead position. The headlights are no longer turned.
- The dipped headlights remain on.



Deactivation of adaptive headlights function in response to system faults
In the event of a system error, the indicator light on the light switch will flash.
Dazzling of oncoming traffic must be prevented in the event of a system fault.
For this reason, the adaptive headlights function is deactivated as follows:
- If the stepper motors are still functional, the headlights are returned to the straight-ahead position. The headlights are no longer moved towards bends in the road.
- If it is no longer possible for a headlight to be moved back to the straight-ahead position, the headlight is tilted downwards (by the stepped motors for automatic headlight-range adjustment). This prevents dazzling of oncoming traffic.
- If the headlight cannot be tilted downwards, the bi-xenon bulb in this headlight is disabled as follows:
When the vehicle is parked up, the control unit registers sleep mode for the adaptive headlights, as follows: Standstill and terminal R OFF for several minutes.
The next time the vehicle is restarted, the bi-xenon light of the defective headlight is not switched on.
The front foglights are switched on in order to ensure a minimum level of illumination.
The dipped headlight is not switched off while the vehicle is in motion.



Setting headlights to parked position
When terminal R is switched off, the headlights move to the parked position. The parked position is important for the headlights' next calibration sequence. From the parked position, the headlights are run through a calibration sequence in the pre-drive-check. During the calibration sequence, the control unit for adaptive headlights relearns the straight-ahead position for the headlights.
When the headlights have reached the parked position, the stepper motor controllers SMCs inform the control unit for adaptive headlights ("verification").
The control unit for adaptive headlights deactivates the stepper motor controllers. The run-down period lasts approx. 10 seconds.



Automatic headlight-range adjustment
If the special equipment "Adaptive headlights" is fitted, the control unit for adaptive headlights also controls the automatic headlight-range adjustment.
The automatic headlight-range adjustment adapts the headlight range for different operating conditions.
Variations in the vehicle tilt angle are produced by vehicle loads and braking or acceleration in extreme driving situations. The automatic headlight-range adjustment moves the headlights up and down as required.

The control unit for adaptive headlights also controls the automatic headlight-range adjustment as follows.
1. The ride-height sensors and the brake light switch supply the signals for the automatic headlight-range adjustment.
2. The control unit for adaptive headlights computes the vehicle inclination (longitudinally to the roadway) from the signals.
3. The stepper motors for the automatic headlight-range adjustment automatically and dynamically control the headlight range.

The headlight range is adjusted so that the actual headlight range conforms to the legally required headlight range as follows:
- If vehicle rear is lower than front:
The actual headlight range will be longer than the legally stipulated range. The headlight beam height is lowered to reduce the headlight range to match the legal requirement.
- If the vehicle is horizontal:
The actual headlight range will be the same as the legally stipulated range.
- If vehicle front is lower than rear:
The actual headlight range will be shorter than the legally stipulated range. The headlight beam height is raised to increase the headlight range to match the legal requirement.



Adaptive headlights for automatic driving lights control
The automatic driving lights control feature (option in conjunction with the rain-light sensor) switches the side lights and dipped headlights on and off automatically.
Switch-on conditions:
- The automatic driving lights control must be encoded in the light switch cluster or light module.
- The light switch must be in position A" ("A" stands for automatic driving lights control and for adaptive headlights).
- The rain-light sensor must be installed and operational.
The rain-light sensor detects the brightness of the ambient light.
The rain-light sensor sends the following prompts to the light switch cluster or the light module:
- Ambient brightness low: In twilight, darkness, in an underground garage or tunnel.
"Switch on dipped headlights" request
- Ambient brightness sufficient.
"Switch off dipped headlights" request
If only the side lights are to be switched on, the light switch must be set to side lights (switch position 1).
When the light switch is set to position "A", the control unit for adaptive headlights is also activated:
- When the automatic driving lights control function switches on the dipped headlights (e.g. at twilight), the adaptive headlights function is notified at the same time.
The control unit for adaptive headlights then assumes control of the automatic headlight-range adjustment.
- In addition, the signals from the rain-light sensor are also evaluated. The headlights are not turned when the vehicle is cornering until total darkness sets in.

The message "dipped headlights on" is given individually for each headlight.
If a headlight fails, the adaptive headlights are switched off.
The front foglights are switched on in order to ensure a minimum level of illumination.



Turning lights
> E83 from 09/06
The turning lights are coupled to the adaptive headlights (option 524).
Depending on actuation, the right-hand and/or left-hand front foglight is switched on. The turning lights are actuated by the light module (LM). The turning light are not switched on suddenly but rather faded according to special time parameters.
Depending on the country concerned, the turning lights are switched on when cornering.

The following conditions must be satisfied for the turning lights to be switched on:
- Terminal 15 ON
- Light switch in position "A" ("A" stands for automatic driving lights control)
- Rain-light sensor detects twilight or darkness (threshold exceeded)
and

- Turn signal indicator ON (not one-touch turn signal)
- Speed range (forwards):
- Europe and Japan version from 0 km/h to 35 km/h
- US version from 0 km/h to 65 km/h
- Swivel angle (theoretical):
- when stationary ≥ 77°
- when driving ≥ 10°
Alternatively
- Speed range (reverse):
- 0 km/h to 35 km/h
- Swivel angle (theoretical):
- when stationary or driving ≥ 70°
If the vehicle is stationary, the turning lights will automatically be deactivated after a certain time, e.g. when waiting at traffic lights. However, the turning lights can be activated again with the turn-signal/main-beam switch.

The light module (LM) uses the following signals to actuate the turning lights:
- Steering angle
- Yaw rate
- Status of reverse gear
The following conditions must be satisfied for the turning lights to be switched off:
- Light switch not in position "A" ("A" stands for automatic driving lights control)
- Rain-light sensor does not detect twilight or darkness (lower threshold exceeded)
Alternatively
- Turn signal indicator OFF
- Speed range (forwards):
- Europe and Japan versions ≥ 40 km/h
- US version ≥ 70 km/h
- Swivel angle (theoretical):
- when stationary 77°
- when driving 10°
Alternatively
- Speed range (reverse): ≥ 40 km/h
- Swivel angle (theoretical): when stationary and when driving below a certain value
Alternatively
- Vehicle skids and swings out.
Alternatively
- Front foglights are switched on with the front foglights switch.

Preconditions for activation
The control unit for adaptive headlights is "awake" from terminal 15 ON.
The movement of the lights is subject to the following conditions:

- Reverse gear must not be engaged.
- No system faults must be present. The indicator light must not be flashing.
- The bulbs for the bi-xenon lights are OK in both headlights.
- The vehicle must not be skidding or fishtailing.
- The rain-light sensor must detect darkness.
- Additional precondition for activation: automatic driving lights control is active (light switch in position "A", see above).

Notes for service staff

Caution: Exercise caution when working on bi-xenon headlights
Whenever inspecting or working on the headlights, always observe the safety precautions and accident prevention rules. The headlight system has dangerously high voltage.

- General note:
- Diagnosis:
- Encoding/programming:
- Car and Key Memory:
The sensitivity of the driving light sensor can be set with the Car and Key Memory.

National versions
The options "Daytime driving lights" and "Manual headlight-range adjustment" are available in certain countries.
Vehicles with manual headlight-range adjustment do not have adaptive headlights.
This is because vehicles with manual headlight-range adjustment have halogen dipped headlights; adaptive headlights are only available in conjunction with option 522 "Xenon dipped and main-beam headlights".



Switching on adaptive headlights in conjunction with daytime driving lights function
The "Daytime lights" option (Northern Europe and Canada) means that
The dipped headlights and the side lights are always switched on under the following conditions:
- Light switch in position "2"
- Terminal 15 ON
The automatic headlight-range adjustment is active (actuated by the control unit for adaptive headlights).
If terminal 15 is switched off, the dipped headlights and the side lights are automatically switched off as well.
The light switch must also be set to position "A" with the "Daytime driving lights" option. The control unit for adaptive headlights is then in standby.
System functions for "Daytime lights" option when the light switch is set to position "A":
- If the vehicle is encoded with the "Daytime driving lights" option (end of production line), the light switch can remain in position "A" at all times.
When terminal R is switched on, side lights, parking lights and licence plate lights are switched on.
As soon as terminal 15 is switched on, the dipped headlights are also switched on.
- When the dipped headlights are switched on, the adaptive headlights control unit is activated (for automatic headlight-range adjustment).
- The indicator lamp on the light switch lights up and indicates that the system is functional.
- The adaptive headlights turn when the vehicle is stationary if the steering wheel is turned (to the right only).
- The headlights are moved when the vehicle corners if the rain-light sensor registers darkness.
The switch-on conditions for the adaptive headlights in conjunction with special equipment "Daytime driving lights" are as follows:
- The vehicle must be encoded with the "Daytime driving lights" option (end of production line)
- The light switch must be in position "A"
- Terminal 15 must be switched on and reverse gear must not be engaged
- Rain-light sensor must detect darkness

Subject to change.