Part 2

63 02 03 007 Adaptive Headlight

System functions
The adaptive headlights system moves headlights horizontal (i.e. from left to right) in order to illuminate the inside of a bend when cornering.

The following system functions of the adaptive headlights system are described below:
- System activation and reference run
- Activation of stepper motor controllers
- Speed-dependent evaluation of signals
- Adjustment of headlight horizontal aim
- Deactivation of adaptive headlights function under extreme driving conditions
- Deactivation of adaptive headlights function in response to system faults
- Setting headlights to parked position
- Automatic headlight beam throw adjustment
- Adaptive headlights for automatic driving lights control
- Cornering light
- Adaptive headlight beam throw adjustment
- Variable light distribution (depending on the national-market version)

NOTE: Different control units for adaptive headlights.
> E60, E61, E63, E64, E65, E66 up to 03/2005: The adaptive headlights are actuated by the AHL control unit.

> E60, E61, E63, E64, E65, E66 up to 03/2005: The adaptive headlights are actuated by the light module (LM).
> E70, E71, E72, E81, E82, E87, E88, E89, E90, E91, E92, E93: The adaptive headlights are controlled by the footwell module (FRM). The footwell module has its own system description. [more in the vehicle engineering diagnosis (SBT) 61 04 04 094]
For this reason, the following text refers to the general "control unit for adaptive headlights".

System activation and reference run
When terminal 15 is switched ON, the headlights always perform a reference run, even if the low-beam headlights are not switched on. The control unit for adaptive headlights transmits the "perform reference run" request to the stepper motor controllers (SMCs, control units for the headlight stepper motors). The stepper motor controllers control the stepper motors in the headlights. The reference run is performed. In the reference run, the headlights move as follows:
1. The headlights move to the right and left (= reference run for adaptive headlights).
2. The headlights move up and down (= reference run for automatic headlight beam throw adjustment).
3. At the end of the reference run, the headlights are in the straight-ahead position.

Following the reference run, the system is operational.
When reverse gear is engaged, the headlights are moved to the straight-ahead position.

NOTE: The reference run is only performed after terminal 15 has been switched OFF for at least 15 seconds.
> E66, E61, E63, E64, E65, E66 until 09/2006
> E87, E90, E91, E92, E93 until 03/2007
If terminal 15 is repeatedly switched on and off (e.g. for demonstration purposes), the reference run will not be executed every time terminal 15 is switched on. Terminal 15 must have been switched off for at least 15 seconds before it is switched on again. Only then is a reference run performed when terminal 15 is switched on.

NOTE: Reference run always after terminal 15 ON and low-beam headlights ON.
> E66, E61, E63, E64, E65, E66 from 09/2006
> E70, E81, E82, E88, E89, from series launch
> E87, E90, E91, E92, E93 from 03/2007
If terminal 15 is repeatedly switched on and off (e.g. for demonstration purposes), the reference run will not be executed every time terminal 15 and the low-beam headlights are switched ON.

NOTE: Reference run with enlarged movement range.
> not E65, E66
From 09/2007, starting with the E60, E61, E63, E64, a reference run with larger movement range will be introduced. The reference run with larger movement range will then gradually be introduced on other model series.

Activation of stepper motor controllers
The control unit for adaptive headlights transmits the stepper motor controllers (SMC) the nominal values for the swivel modules (position of swivel modules and speed of movement).
The control unit for adaptive headlights calculates the nominal values using the following signals:
- Driving 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 evaluation of signals
Depending on the driving speed, the adaptive headlights are controlled using the following signals: Signals from the steering angle sensor and signals from rotation-rate sensor (in the DSC sensor).
The encoding (at the end of line) determines the priority assigned to sensor signals above which speed threshold.

Adjustment of headlight horizontal aim
The stepper motor controllers move the headlights to the right or left when the vehicle corners.
Horizontal movement range of headlights:
- Inwards, i.e. towards centre of vehicle: up to max. 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).

Viewed from the vehicle, the right-hand headlight moves "outwards".
The left-hand headlight moves up to 8� (the left-hand headlight moves towards the centre of the vehicle, i.e. "inwards" as viewed from the vehicle).
The headlight on the outside of the bend has to reach its end position at the same time as the headlight on the inside of the bend so that the carriageway remains smoothly and 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 driving 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 low-beam headlights remain on.

Deactivation of adaptive headlights function in response to system faults
Until 09/2007, a system fault will be indicated by the indicator light on the light switch flashing.
From 09/2007 system fault will be indicated by a Check Control message in the instrument panel.
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 lowered (by the stepper motors for automatic headlight beam throw adjustment). This prevents dazzling of oncoming traffic.
- Vehicles up to 09/2007: If the headlight cannot be lowered, the bi-xenon bulb in this headlight is disabled as follows:
When the vehicle is parked up, the control unit registers rest state for the adaptive headlights, as follows: Vehicle 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 fog lights are switched on in order to ensure a minimum level of lighting.
The low-beam headlights are not switched off while the vehicle is in motion.

NOTE: From 09/2007, the low-beam headlights will not be switched off in the event of a system fault.
From 09/2007, the low-beam headlights will not be switched off in the event of a system fault.

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 reference run: From the parked position, the headlights are run through a reference run in the pre-drive check. During each reference run 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 ("confirmation").
The control unit for adaptive headlights deactivates the stepper motor controllers.
The after-running period lasts approx. 10 seconds.

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

The control unit for adaptive headlights also controls the automatic headlight beam throw adjustment as follows:
1. The ride height sensors and the brake light switch supply the signals for the automatic headlight beam throw 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 beam throw adjustment automatically and dynamically control the headlight beam throw.
The headlight range is adjusted so that the actual headlight beam throw conforms to the legally required headlight beam throw as follows:
- If vehicle rear is lower than front: The actual headlight beam throw will be longer than the legally stipulated headlight beam throw. The headlight beam throw is lowered to reduce the headlight beam throw to match the legal requirement.
- If the vehicle is horizontal: The actual headlight beam throw will be the same as the legally stipulated headlight beam throw.
- If vehicle front is lower than rear: The actual headlight beam throw will be shorter than the legally stipulated headlight beam throw. The headlight beam throw is raised to increase the headlight beam throw to match the legal requirement.

Adaptive headlights for automatic driving lights control
The automatic driving lights control feature (optional equipment in conjunction with the rain/light sensor) automatically switches the side lights and low-beam headlights on or off.
Switch-on conditions:
- The automatic driving lights control must be encoded (in the light module on the E60, E61, E63, E64, E65, E66 , in the footwell module on the E70, E71, E72, E81, E82, E87, E88, E89, E90, E91, E92, E93).
- The light switch position must be A ( A for automatic driving lights control and adaptive headlights).
- The rain/light sensor must be installed and operational.
The rain/light sensor detects the ambient brightness.
The rain/light sensor transmits the following requests to the light module (on the E70, E71, E72, E81, E82, E87, E88, E89, E90, E91, E92, E93: footwell module):
- Ambient brightness low: In twilight, darkness, in an underground garage or tunnel.
"Switch on low-beam headlights" request

- Ambient brightness sufficient.
"Switch off low-beam 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 position is set to A , the control unit for adaptive headlights is also activated:
- When the automatic driving lights control function switches on the low-beam headlights (e.g. at dawn/dusk), the adaptive headlights function is notified at the same time.
The control unit for adaptive headlights thus assumes control of the automatic headlight beam throw adjustment.

- The signals from the rain/light sensor are also evaluated (E60, E61, E63, E64, E65, E66: by the light module; E81, E82, E87, E88, E90, E91, E92, E93: by the footwell module).
The headlights are not turned when the vehicle is cornering until total darkness sets in.

The message low-beam headlights on is given individually for each headlight.
If a headlight fails, the adaptive headlights are switched off. The front fog lights are switched on in order to ensure a minimum level of lighting.