Lights - Service Information BMW M3 E46

Scheme 1

Launch schedule for "Adaptive headlights" option 524

1. E46 Coupe (E46/2) and E46 Convertible (E46/C) model revision: 03/2003
2. E60: 03/2003. Adaptive headlights are approved for the European market, for United Kingdom and the US from the start of series production of the E60 (07/2003). This is also the case for Japan and Taiwan.
3. E65, E63, E83: From 10/2003 E83 US version: "Xenon lights without AHL" option 522 will be available from E83 EURO: "Xenon lights without AHL" option 522 will be available from 09/2004.
4. E53: 04/2004 onwards

Note. Option 524 is only available in conjunction with option 522. "Adaptive headlights" option 524 is only delivered in conjunction with "Bi-xenon main and dipped beam headlights" option 522.

Note. EU approval for option 522 only in conjunction with option 502. "Bi-xenon main and dipped beam headlights" option 522 "is only delivered in conjunction with "Headlight cleaning system" option 502 (in countries with EU approval).

Note. AHL = ALC The development designation for the adaptive headlights was "ALC". ALC was the abbreviation for "Adaptive Light Control". The marketing and sales designation for option 524 in English-language markets is "adaptive headlights", abbreviated to "AHL". This is why the abbreviation "AHL" is used even in diagnostics and technical vehicle documentation. However, some control units may still bear the abbreviation "ALC", which may also be the abbreviation used in the EPC (Electronic Parts Catalogue).

Introduction

The adaptive headlights system turns the bi-xenon headlights towards the inside of a bend

when cornering. This improves illumination of the curve of the road.

Visibility is therefore improved.

When cornering, the driver is not looking into a "black hole" - instead, the adaptive headlights allow the driver to see the curve of the road. For more information, refer to E46 SYSTEM OVERVIEW OF ADAPTIVE HEADLIGHTS .

Brief description of components

The following components and control units provide input signals for the adaptive headlights system

1. Light switches on the light switch cluster The rotary switch for the side lights and dipped beam headlights differs depending on the vehicle equipment level (adaptive headlights, automatic driving lights control, automatic or manual headlight-range adjustment). For the adaptive headlights function to operate, the light switch must be set to position "A" ("A" = "automatic driving lights control" or "adaptive headlights"). For more information, refer to «E46 LIGHT SWITCH ON THE LIGHT SWITCH CLUSTER»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-light-switch-on-the-light) .
2. Direction indicator/main beam switch The main beam headlights are switched on and off with the direction indicator/main beam switch (by pressing or pulling the switch). The adaptive headlights function operates with both dipped and main beam headlights. For more information, refer to «E46 - DIRECTION INDICATOR/MAIN BEAM SWITCH»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information) .
3. Ride-height sensors The ride-height sensors supply the input signals for the headlight-range adjustment. There is one ride-height sensor located on the right-hand side of the front axle. There is one ride-height sensor located on the right-hand side of the rear axle. Automatic headlight-range adjustment adjusts the vertical aim of the headlights to compensate for variations in the vehicle tilt angle (e.g. when the vehicle is laden, and under braking and acceleration when the vehicle is in motion). If the vehicle is equipped with the "adaptive headlights" option, the control unit analyses the signals from the ride-height sensors for the adaptive headlights (AHL control unit). This is because: The AHL control unit also controls automatic headlight-range adjustment. For more information, refer to «E46 RIDE-HEIGHT SENSORS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-ride-height-sensors) .
4. Brake light switch If the vehicle is equipped with the "adaptive headlights" option, the signals from the brake light switch are read by the control unit for the adaptive headlights. The signal sent by the brake light switch is an input signal for the automatic headlight range adjustment; see RIDE-HEIGHT SENSORS.
5. Zero-position sensor (E46, E63, E83) The zero-position sensor in the AHL headlight sends a signal for calculating the zero position of the AHL headlight. This regulates the horizontal movement of the AHL headlight. For more information, refer to «E46, E63, E64, E83, E90 - ZERO-POSITION SENSOR»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-e63-e64-e83-e90) .
6. Basic module The basic module supplies input signals with regard to the terminal management (terminal 15 ON). The adaptive headlights control unit is activated when terminal 15 is switched ON.
7. EGS control unit or reversing light switch When reverse gear is engaged, the headlights are moved to the straight-ahead position. For automatic transmissions, the EGS (electronic transmission control) sends the appropriate signal to the light module; for manual transmissions, the reversing light switch sends the signal.
8. KOMBI (control unit in the instrument cluster): The instrument cluster control unit is the gateway (i.e. data interface) between the PT CAN data bus and the K bus. The signals from the EGS control unit and the DSC control unit (see below: DSC sensor) are sent via the KOMBI control unit to the control unit for the adaptive headlights.
9. Rain-light sensor for automatic driving lights control (option) The rain-light sensor measures the ambient light conditions outside the vehicle. In twilight, the rain-light sensor sends the request "Twilight" to the light switch cluster. The light switch cluster sends the relevant information to the adaptive headlights control unit which enables the automatic headlight-range adjustment of the dipped beam headlights to be activated. The headlights are tilted up and down as required, but they are not swivelled towards the bend in the road. In darkness, the rain-light sensor sends the message "Darkness" to the light switch cluster. The light switch cluster sends the relevant information to the adaptive headlights control unit. The headlights are swivelled towards the bends in the road as required. For more information, refer to «E46 - RAIN-LIGHT SENSOR»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-rain-light-sensor) .
10. Steering angle sensor and DSC sensor The steering angle sensor and DSC sensor (DSC = Dynamic Stability Control) supply signals for the adaptive headlights to the adaptive headlights control unit. These signals are evaluated as follows, depending on the vehicle's speed: Vehicle speeds up to 30 km/h: The adaptive headlights function is controlled on the basis of the information from the steering angle sensor (in the steering column switch cluster). Vehicle speeds between 30 km/h and 50 km/h: In the 30 to 50 km/h speed range, there is a continuous transition in signal evaluation: from the evaluation of signals sent by the steering angle sensor to evaluation of the signals sent by the yaw rate sensor (in the DSC sensor). Signals from the yaw rate sensor are evaluated in extreme dynamic driving situations , e.g. if the vehicle starts to skid or fishtail, even at speeds of less than 50 km/h. If the vehicle starts to skid or fishtail, the headlights will move to the straight-ahead position. The headlights are not swivelled until the vehicle has stabilized. Vehicle speeds over 50 km/h: At speeds upwards of 50 km/h, the signals from the yaw rate sensor (in the DSC sensor) form the primary basis for control of the adaptive headlights function. Reason: for a constant cornering radius, the steering angle required increases over proportionally with increasing speed. In addition, the steering angle required also depends on the friction coefficient of the carriage way. The yaw rate is directly proportional to speed. For this reason, the yaw rate is always the most suitable measure for controlling the adaptive headlights at high speeds. Even at high speeds, however, the steering angle sensor signal is used to detect in advance (predict) the driver's commands. This is because: The yaw rate signal is not supplied until the vehicle has responded to the steering wheel movement. There is no signal output by steering angle sensor in the event of sudden, rapid steering wheel movements (surging) to prevent these from influencing the function of the adaptive headlights. A number of control units are involved in the adaptive headlights system (see GM, EGS, KOMBI). In a narrower sense, the following control units are involved in the adaptive headlights function
11. AHL control unit For safety reasons, the AHL control unit is also responsible for the automatic headlight range adjustment. The following fault is conceivable: after swivelling, one headlight remains in a position that is dazzling to oncoming traffic. As a result, the AHL control unit attempts to tilt this headlight downwards (using the stepper motors for the automatic headlight-range adjustment). If the headlight cannot be tilted downwards, the bi-xenon bulb in this headlight is disabled. Conditions for disablement: The vehicle must have been parked (vehicle stationary and terminal R OFF for several minutes). The AHL control unit is connected to the K bus. For more information, refer to «E46 - AHL CONTROL UNIT FOR ADAPTIVE HEADLIGHTS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-ahl-control-unit-for) .
12. Stepper motor controllers The stepper motor controllers (SMC) control the stepper motors in the headlights (for the automatic headlight-range adjustment and for the adaptive headlights)., For more information, refer to «E46 STEPPER MOTOR CONTROLLERS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-stepper-motor-controllers) .
13. LSZ control unit The LSZ control unit (light switch cluster) forwards requests from the light switch and the direction indicator/main beam switch to the AHL control unit (on the K bus). For more information, refer to «E46 LSZ CONTROL UNIT»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-lsz-control-unit) .
14. Xenon-headlight control unit The xenon-headlight control unit monitors the D2-S bulbs for the bi-xenon headlights. For more information, refer to «E46 - BI-XENON HEADLIGHTS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-bi-xenon-headlights) . The following components are controlled
15. Stepper motors for the adaptive headlights Are located in the headlight units. For more information, refer to «E46 - HEADLIGHTS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-headlights) . The stepper motors turn the swivel modules in the bi-xenon headlights. The stepper motors swivel the headlights along the vertical and horizontal axes. (vertical = up and down for the automatic headlight-range adjustment; horizontal = to the left and right for the adaptive headlights).
16. Green indicator light on the light switch cluster The green indicator lamp next to the "A" ("A" stands for "Automatic driving lights control" or for "Adaptive headlights") has two display functions: The LED lights up permanently when the automatic driving lights control/adaptive headlights function is switched on (= light switch in position "A"). The LED flashes if a fault develops in the adaptive headlight system. For more information, refer to «E46 - ADAPTIVE HEADLIGHTS (AHL), DIAGNOSTICS»(/bmw/m3/e46-1999-2006/remont/exterior-lights/#lights-service-information__e46-adaptive-headlights-ahl-diagnostics) . The green indicator lamp (LED) is actuated by the light switch cluster.

Note. Components for the AHL on the E53

1. Similarities with the E46: The E53 has the same vehicle electrical system as the E46. The E53 uses the LSZ (light switch cluster) control unit for controlling the exterior lights (as does the E46).
2. Similarities with the E60: The E53 has a position sensor (as does the E60) instead of a zero-position sensor (= E46).

Note. Components for the AHL on the E63

1. Similarities with the E60: The E63 has the same vehicle electrical system as the E60. The E63 uses the LM (light module) control unit for controlling the exterior lights (as does the E60).
2. Similarities with the E46: The E63 has a zero-position sensor (as does the E46).

System functions

The adaptive headlights system adjusts the horizontal aim of the headlights (i.e. from side to side) in order to illuminate the inside of a bend when cornering.

The following functions of the adaptive headlights system are described below

1. System activation and calibration sequence
2. Activation of stepper motor controllers (SMC)
3. Speed-dependent analysis of input signals
4. Horizontal swivelling of the headlights by the stepper motor controller
5. Deactivation of adaptive headlight movements under extreme driving
6. Deactivation of adaptive headlight movements in response to system faults
7. Setting headlights to parked position
8. Activation of automatic headlight-range adjustment by the AHL control unit
9. Adaptive headlights for automatic driving lights control System activation and calibration sequence When terminal 15 is switched ON, the headlights always perform a calibration sequence, even if the lights are not switched on. The AHL control unit sends the "perform calibration sequence" request to the stepper motor controllers (SMC = control unit for the headlight stepper motors). The stepper motor controllers actuate the stepper motors in the headlights. The calibration sequence is performed. During the calibration sequence, the headlights move in the following manner: The headlights move horizontally (= calibration sequence for the adaptive headlights ). The headlights move vertically (= calibration sequence for the headlight-range adjustment function). At the end of the calibration sequence, the headlights are in the straight-ahead position. Following the calibration sequence, the system is ready for operation. When reverse gear is engaged, the headlights are moved to the straight-ahead position.

Note. The calibration sequence is performed only after terminal 15 has been switched OFF for at least 15 seconds.

If terminal 15 is switched on and off repeatedly (for example, for demonstration reasons), the headlights are not calibrated each time terminal 15 is switched on.

Terminal 15 must have been switched off for at least 15 seconds before it is switched on. Only then is a calibration sequence performed when terminal 15 is switched on again.

Activation of stepper motor controllers

The AHL control unit sends the reference values for the swivel modules (values relating to the position of the swivel modules and the speed of swivel movement) to the stepper motor controllers. The AHL control unit calculates the nominal values on the basis of the following input signals

1. Car road speed
2. Steering angle (at speeds up to 50 km/h, depending on programming)
3. Yaw rate (50 km/h upwards, see "Steering angle sensor and DSC sensor" above)

Speed-dependent analysis of input 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 coding (at the end of the production line) determines the priority assigned to sensor signals above which speed threshold (see above).

Horizontal swivelling of the headlights by the stepper motor controller

Horizontal range of movement of headlights

1. Inwards, i.e. towards center of vehicle: through a maximum of 7° (for E46, E83, E63)
2. Outwards: through a maximum of 15°

This means, for example, that on a right-hand bend

the right-hand headlight swivels through a maximum of 15° (since the right-hand headlight is on the inside of the bend and therefore swivels outwards away from the vehicle center).

The left-hand headlight swivels through a maximum of 7° (the left-hand headlight swivels towards the vehicle center, i.e. inwards).

The headlight on the outside of the bend reach its end position at the same time as the headlight on the inside of the bend.

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 headlight movements under extreme driving conditions

If the vehicle starts to skid and fishtail, the swivelling movement of the adaptive headlights is deactivated as follows

1. The headlights are returned to the straight-ahead position. The headlights are no longer swivelled.
2. The lights remain on.

Deactivation of adaptive headlight movements in response to system faults

The green indicator light on the light switch cluster flashes if a system fault is present.

Dazzling of oncoming traffic must be prevented in the event of a system fault.

To this end, the swivelling movement of the adaptive headlights is deactivated as follows

1. If the stepper motors are still functional, the headlights are returned to the straight-ahead position. The headlights are no longer swivelled towards bends in the road.
2. 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.
3. If the headlight cannot be tilted downwards, the bi-xenon bulb in this headlight is disabled as follows: When the vehicle is parked, idle status (sleep mode) is detected by the AHL control unit (vehicle stationary and terminal R OFF for several minutes). The bi-xenon bulb in the defective headlight is not switched on when the engine is restarted. The front fog lights are switched on in order to ensure a minimum level of illumination. The dipped beam headlights are 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 this calibration sequence, the AHL control unit learns the straight-ahead position for the headlights once again.

When the headlights have reached the parked position, the stepper motor controllers (SMCs) inform the AHL control unit ("acknowledge"). The AHL control unit deactivates the stepper motor controllers. The post-run time (= the time between "acknowledge" and "switch off") is approximately 10 seconds.

Activation of automatic headlight-range adjustment by the AHL control unit

If the vehicle is equipped with the "adaptive headlights" option, the AHL control unit also controls the automatic headlight-range adjustment.

The automatic headlight-range adjustment adjusts the vertical aim of the headlights to compensate for variations in the vehicle tilt angle. Variations in the vehicle tilt angle are produced by vehicle loads and braking or acceleration in extreme driving situations. The automatic headlight-range adjustment tilts the headlights up and down as required.

The AHL control unit controls the automatic headlight-range adjustment as follows

1. The ride-height sensor and the brake light switch send the input signals for the headlight-range adjustment to the AHL control unit.
2. From the input signals received, the AHL control unit calculates the vehicle tilt angle (along the longitudinal axis, relative to the road surface).
3. The vertical aim of the headlights is controlled automatically and dynamically by the stepper motors for swivelling the headlights along the vertical axis. The actual headlight range is adjusted to the legally specified headlight range as follows: If vehicle is lower at the rear than at the front: The actual headlight range will be longer than the legally specified range. The vertical aim is lowered to reduce the headlight range to meet the legal requirement. If the vehicle is perfectly horizontal: The actual headlight range will be the same as the legally specified range. If the vehicle is lower at the front than the rear: The actual headlight range will be shorter than the legally specified range. The vertical aim is raised to increase the headlight range to meet 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 beam headlights on and off automatically.

Switch-on conditions

1. The light switch cluster must be coded with automatic driving lights control.
2. The light switch must be in position "A" ("A" for automatic driving lights control and the adaptive headlights).
3. 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 requests to the light switch cluster: low ambient brightness (twilight, darkness, in a low-level garage or tunnel): "switch on dipped beam headlights" request sufficient ambient brightness: "switch off dipped beam headlights" request If only the side lights are to be switched on, the light switch must be set to side lights (position 1).

When the light switch is set to position "A", the AHL control unit is also activated

1. When the automatic driving lights control function switches on the dipped beam headlights (e.g. at dawn/dusk), the adaptive headlights function is notified at the same time. The light switch cluster sends the message "Dipped headlights on" to the AHL control unit (and the AHL control unit assumes control of the automatic headlight-range adjustment).
2. The control module for the exterior lighting also evaluates the signals from the rain - light sensor (LSZ = light switch cluster or LM = light module for E60, E53). The headlights are not turned when the vehicle is cornering until total darkness sets in.

The message "Dipped headlights on" is generated separately for each headlight unit.

If one of the headlights fails, the turning movement of the adaptive headlights is deactivated.

The front fog lights are switched on in order to ensure a minimum level of illumination.

Switch-on conditions

Beginning with terminal 15 ON, the AHL control unit "wakes up". The swivelling of the lights is subject to the following conditions

1. Reverse gear must not be engaged.
2. No system faults must be present. The indicator lamp must not be flashing.
3. The D2-S bulbs in both headlight units must be working (the D2-S bulbs are the bulbs for the xenon headlights).
4. The vehicle must not be skidding or fishtailing.
5. The rain-light sensor must detect darkness.
6. Additional switch-on condition: automatic driving lights control is active (light switch in position "A", see above).

Notes for service staff

When inspecting or working on the headlights, always observe the safety precautions and accident prevention rules. The headlight system carries dangerously high voltages.

National versions

The "Daytime driving lights" and "Manual headlight-range adjustment" equipment are available in certain countries.

Vehicles with manual headlight-range adjustment do not have adaptive headlights (since vehicles with manual headlight-range adjustment have halogen bulbs for the dipped beam headlights; adaptive headlights are only available on vehicles with the "bi-xenon lights" option).

Activating adaptive headlights in conjunction with daytime driving lights

The "Daytime driving lights" option (Northern Europe and Canada) means that

The dipped beam headlights and the side lights are always switched on under the following conditions

1. light switch in position "2"
2. terminal 15 ON

The automatic headlight-range adjustment function is active (controlled by the AHL control unit).

If terminal 15 is switched off, the dipped beam headlights and the side lights are automatically switched off as well.

The light switch must be in position "A" even on vehicles with the "Daytime driving lights" option to enable the adaptive headlights to operate.

System functions for "Daytime lights" option when the light switch is set to position "A"

1. If the vehicle is coded 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, the side lights, locator lighting and licence plate lighting are switched on. When terminal 15 is switched on, the dipped beam headlights are also switched on.
2. When the dipped beam headlights are switched on, the adaptive headlights control unit is enabled at the same time (for headlight headlight-range adjustment).
3. The green indicator light on the light switch cluster lights up, indicating that the system is operational.
4. The adaptive headlights turn when the vehicle is stationary if the steering wheel is turned (to the right only).
5. If darkness is detected (= signal from rain-light sensor) the headlights are turned when the vehicle is cornering.

The switch-on conditions for the adaptive headlights in conjunction with the "Daytime driving lights" option are as follows

1. The vehicle must be coded with the "Daytime driving lights" option (end of production line)
2. The light switch must be in position "A"
3. Terminal 15 must be switched on and reverse gear must not be engaged
4. The rain-light sensor must detect darkness

Subject to change.

E46 System overview of adaptive headlights

This system overview contains

1. Input/output
2. System circuit diagram
3. Overview of the signal paths for the adaptive headlights

Scheme 2

INPUT AND OUTPUT LEGEND

Scheme 3

SYSTEM CIRCUIT DIAGRAM LEGEND

Overview Of The Signal Paths For The Adaptive Headlights

The instrument cluster control unit is the gateway (i.e. data interface) between the PT CAN data bus and the K bus. Signals from the EGS control unit and the DSC control unit are sent to the adaptive headlights control unit via the instrument cluster control unit.

The signal paths between the individual control units are represented in the following illustration

Scheme 4

Signal Paths For Adaptive Headlights Legend

Signal Path For "Switch On Dipped Beam Headlights"

When terminal 15 is switched ON (signal from basic module via the K bus to the light switch cluster) the dipped beam headlights are switched on at switch position 2. Signal path

GM -> K bus -> LSZ and AHL and AHM (basic module -> body bus -> light switch cluster and AHL control unit and trailer module)

and

Switch position 2 on the LSZ -> K bus -> AHL and the AHM (light switch cluster -> body bus -> adaptive headlights and trailer module)

Signal Path For "Activate Adaptive Headlights"

When terminal 15 is switched ON (signal from the basic module via the K bus to the light switch cluster) and the light switch is in position "A", the adaptive headlights control unit is enabled. Signal path

LSZ -> K bus -> AHL

Signal Path For "Swivel Headlights" For Adaptive Headlights

1. 1. Switch-on condition "Light switch in position A" present. Signal path: LSZ -> K bus -> AHL
2. Switch-on condition "terminal 15 ON" present. Signal path: GM -> K bus -> LSZ and AHL
3. Switch-on condition "dark" present. Signal path: RLS -> K bus -> AHL
4. Switch-on condition "Cornering" present. Signal path: Steering angle sensor in the MFL -> K bus -> AHL or yaw rate sensor in DSC sensor -> suspension CAN -> DSC -> PT CAN -> KOMBI -> K bus AHL
5. Switch-on condition "Reverse gear not engaged" present. Signal path: EGS -> PT CAN -> KOMBI -> AHL

Signal Path For Adaptive Headlights Calibration Sequence

The calibration sequence is always performed when terminal 15 is switched on (light switch in position "0" or "2" (dipped beam headlights) or in position "A", for example).

Signal path

GM -> K bus -> LSZ and AHL -> LIN -> SMC (basic module -> body bus -> light switch cluster and adaptive headlights -> local bus -> stepper motor controller)

Note. The calibration sequence is performed only after terminal 15 has been switched OFF for at least 15 seconds. If terminal 15 is switched on and off repeatedly (e.g. for demonstration reasons), the headlights are not calibrated each time terminal 15 is switched on. Terminal 15 must have been switched off for at least 15 seconds before it is switched on. Only then is a calibration sequence performed when terminal 15 is switched on again.

Note. AHL = ALC The development designation for adaptive headlights was "ALC", which was the abbreviation for "Adaptive Light Control".

The marketing and sales designation for option 524 in English-speaking countries is "adaptive headlights", abbreviated to "AHL".

In fault-diagnostics contexts and in technical documentation, the system is referred to as "adaptive headlights" and the abbreviation "AHL" used for the control unit.

However, some control units are still marked "ALC".

E46 Light Switch On The Light Switch Cluster

The rotary switch for the side lights and the dipped beam headlights is part of the light switch cluster.

The light switch cluster differs depending on the vehicle equipment level (adaptive headlights, automatic driving lights control, dynamic or manual headlight-range adjustment).

Scheme 5

Installation location

The light switch is located on the outside left in the instrument panel (on the light switch cluster).

Layout

The rotary switch switches on the following

1. Side lights (switch position 1)
2. Dipped beam headlights (switch position 2)
3. "A" for "automatic driving lights control" or "adaptive headlights"

The following variations are possible depending on the vehicle equipment level and the national version

1. Green indicator lamp and switch position "A" on the light switch: The light switch has an additional "A" position and a green indicator lamp (LED) for the automatic driving lights control or the adaptive headlights.
2. Light switch cluster WITHOUT thumbwheel: Vehicles with bi-xenon and automatic headlight-range adjustment do not need a thumbwheel for the headlight-range adjustment
3. Light switch cluster WITH thumbwheel: Vehicles with halogen headlights and manual headlight-range adjustment have a thumbwheel for manual headlight-range adjustment.

The direction indicator/main beam switch is to the left of the steering wheel.

The direction indicator/main beam switch consists of the steering column switch with onboard computer button (for changing the display of time, outside temperature, average consumption, range and average speed on the instrument panel).

Scheme 6

DIRECTION INDICATOR/MAIN BEAM SWITCH LAYOUT LEGEND

E46 Ride-Height Sensors

The ride-height sensors supply the input signals for the headlight-range adjustment.

The automatic headlight-range adjustment feature adjusts the vertical aim of the headlights to compensate for variations in the vehicle tilt angle (e.g. when the vehicle is laden, and under braking and acceleration in dynamic driving situations).

Scheme 7

The ride-height sensors are installed on the front and rear axles as follows

1. Front axle: 1 ride-height sensor on the transverse link, front right
2. Rear axle: 1 ride-height sensor on the pendulum support, rear right

The ride-height sensors for the headlight headlight-range adjustment are always built into ONE side of the vehicle (for example, front right and rear right). If the ride-height sensors were installed diagonally (e.g. front right and rear left), transverse movements of the vehicle would have an effect on the headlight headlight-range.

The ride-height sensors are Hall sensors.

How It Works

The ride-height sensors for automatic headlight-range adjustment feature send voltage signals to the AHL control unit as follows: as the springs are compressed, the output voltage of the ride-height sensors changes linearly.

E46, E63, E64, E83, E90 - Zero-Position Sensor

The position of the positioner modules for the adaptive headlights is detected by the following sensors depending on the model concerned

1. Position sensor (headlights manufactured by Hella) on E60, E61, E65, E66, E53
2. Zero-position sensor (headlights manufactured by Automotive Lighting, previously Bosch) in the E46, E63, E64, E83, E90

Zero-Position Sensor

The zero-position sensor records the zero position of the positioner module for the adaptive headlights as follows: If the positioner module drives past the zero-position sensor, the zero-position sensor signals a level change (between high and low).

The zero-position sensor is crucial for the operation of the positioner modules

1. When the vehicle is parked, the headlights drive to parked position (for terminal 15 OFF).
2. Before the vehicle is driven, the headlights always perform a calibration sequence. During the calibration sequence, the headlights are moved from the parked position past the zero-position sensor and into the straight-ahead position.
3. The zero-position sensor fails, the position of the headlights is determined via a mechanical reference point as follows: The positioner module moves as far as the permitted mechanical end stop and then into the straight-ahead position. The adaptive headlights function is then deactivated. The indicator lamp on the light switch (light switch cluster on the E46) flashes.

The zero-position sensor is installed on the positioner module of the AHL headlight.

Construction

The zero-position sensor is a Hall sensor.

The zero-position sensor works as follows

1. Power supply from the SMC (stepper motor controller): 5 volts (+/- 10 %).
2. Overvoltage protection: The overvoltage protection of the zero-position sensor is located in the SMC.
3. Adaptation to the positioner module: The zero-position sensor is reset manually to adapt to the positioner module (end-of-production-line test by the manufacturer).
4. Replacement value for the zero-position sensor: if the zero-position sensor fails, the headlights are aligned with a mechanical reference point (with a tolerance of up to +/- 1°).

Level Curve Of The Zero-Position Sensor: Level Change Between High And Low

The level curve of the output signal corresponds to the degree of overlap of the Hall sensor and the sensor plate.

The output signal is either a high level signal or a low level signal. The level curve is illustrated in the following graphic

Scheme 8

LEVEL CHANGE BETWEEN HIGH AND LOW LEGEND

E46 - Rain-Light Sensor

The rain-light sensor detects water on the windscreen and the ambient brightness. The signals of the rain-light sensor control the wiper function, the automatic driving lights control and the adaptive headlights control unit.

Scheme 9

The rain-light sensor is located on the windscreen in the base of the interior rear-view mirror.

The rain-light sensor is an optical system consisting of the rain sensor, the driving lights sensor and an electronic evaluation unit.

The rain sensor comprises

1. Optical element: the optical element is affixed to the windscreen.
2. Electronics unit: the electronics unit houses 4 optical transmitter and 4 receiver diodes in addition to the evaluation electronics.
3. Heating: an integrated heating system prevents the optical element and the diodes from misting over.

The driving light sensor consists of 2 photodiodes and an electronic evaluation unit.

Rain Sensor

The rain sensor is activated as follows

1. Terminal R ON (ignition key position 1)
2. Wiper lever in position 1
3. Briefly rotate the rotary dial (on the wiper lever) or clean the windshield (pull the wiper lever).

The rain sensor works as follows

1. A single wipe cycle is performed to provide a visual indication that the rain sensor has been activated.
2. The transmitter diodes emit an infrared beam. The infrared beam is directed onto the windscreen by the optical element.
3. When the windscreen is completely dry and clean, the infrared beam will be completely reflected to the receiver diodes.
4. If the part of the windscreen near the optical element is wet or covered (water, snow, dirt), the infrared beam can no longer be fully reflected. Only a certain fraction of the beam will be able to penetrate the windscreen, which means that only a fraction of the beam will reach the receiver diodes.
5. The electronic evaluation unit then detects the degree of wetness of the windscreen based on the fraction of beam received. The evaluation electronics unit sends a signal to the basic module via the K bus data bus. The basic module triggers a wiper cycle.

The sensitivity of the rain sensor can be adjusted to one of 4 sensitivity settings using the thumbwheel on the wiper switch. Each time the thumbwheel is moved to "Increase sensitivity" (thumbwheel turned up), a wipe cycle is performed.

Sensitivity is automatically reduced when the vehicle is stationary: the wiper usually works in intermittent mode.

In very heavy rain, intermittent mode switches to permanent wipe mode.

If the rain sensor fails, the windscreen wiper will operate with a fixed sweep interval.

When terminal R is switched off, the rain sensor is also switched off.

Preconditions for fault-free operation of the rain sensor are

1. No smears on the windscreen
2. Wiper blades not damaged
3. Windscreen free of faults in area of rain sensor
4. Optical element is affixed to the windscreen free of bubbles.

Initialisation of rain sensor: due to the optical technology involved, the rain sensor must be calibrated to the windscreen: the rain sensor is calibrated to the windscreen during initialisation.

Driving Light Sensor

The driving light sensor works as follows

1. The two photodiodes record the light incidence from the front (frontal light intensity) and from above (surrounding brightness). (The photodiodes work when terminal R is ON, regardless of whether or not the automatic driving lights control is switched on).
2. If the lighting conditions change, the driving light sensor sends a signal via the K bus data bus to the light switch cluster.
3. The light switch cluster switches the driving lights on or off (precondition is that the automatic driving lights control is switched on).
4. If the rain-light sensor detects darkness, the adaptive headlights are also activated and the headlights turn when the vehicle corners. The threshold values from which the rain-light sensor detects "darkness" are stored in the rain-light sensor.

The driving lights sensor is coded with the coding data for the series during the coding procedure.

The sensitivity of the driving light sensor can be set to one of 2 settings with the Car & Key Memory.

E46 - AHL Control Unit For Adaptive Headlights

The AHL control unit is an identical component on all vehicle models with option 524.

The AHL control unit is adapted to the model concerned by coding at the end of the production line (the AHL control unit supplied by the manufacturer is coded for the E60).

The AHL control unit is the master control unit for the vertical and horizontal adjustment of the headlights. The AHL control unit sends the preset values for the position and the speed of the swivelling motion to the stepper motor controllers (in the headlight housing). The stepper motor controllers then control the stepper motors for the headlights accordingly.

The AHL control unit is installed in the carrier behind the glove compartment.

The illustration shows the AHL control unit with the conventional components for the adaptive headlights system

1. Adaptive headlights block diagram
2. Pin assignment

Adaptive Headlights Block Diagram

The following block diagram shows the following relationships

1. Components in the headlights controlled by the central light switch (LSZ) and the AHL control unit.
2. Components supplying the input signals necessary for this.
3. Buses and direct wire connections.

Scheme 10

Note. ADAPTIVE HEADLIGHTS BLOCK DIAGRAM LEGEND Key Explanation Key Explanation 1 AHL control unit for adaptive headlights 2 Stepper motor controller (SMC) 3 Swivel module 4 Xenon control unit and electronic ballast for D2-S bulbs, actuated by the light switch cluster. 5 Light switch cluster (LSZ) 6 Control unit in the instrument cluster (KOMBI) as gateway (= data interface) between the K CAN and PT CAN 7 PT CAN to the basic module (GM) and electronic transmission control (EGS) 8 Light switch 9 Rain/light sensor (RLS) 10 Brake-light switch (brake pedal highlighted in black) 11 Ride-height sensors (one each on front axle, right and rear axle, right) K bus Body bus LIN bus Local bus (Local Interconnect Network) PT CAN Powertrain CAN

Pin Assignment For X10513, 18-Pin Multi-Pin Connector

PIN ASSIGNMENT FOR X10513, 18-PIN MULTI-PIN CONNECTOR

The AHL control unit uses dynamic driving data to calculate the movements of the adaptive headlights and the automatic headlight-range adjustment.

The AHL control unit must be coded with the vehicle-specific data.

Vehicle-specific data includes, for example

1. Wheelbase
2. Height of headlights
3. Data for the headlight headlight-range adjustment (characteristic curve)

Data specific to the headlights is coded in the SMC (stepper motor controller).

E46 Stepper Motor Controllers

The stepper motor controllers (SMC) control the movement of the swivel modules in the bi-xenon headlights as follows

1. Vertically for the automatic headlight-range adjustment (stepper motor for automatic headlight-range adjustment)
2. Horizontally for the adaptive headlights (stepper motor for adaptive headlights)

The stepper motor controllers are affixed to the headlight housing.

The block diagram shows the stepper motor controller and its connections.

To differentiate between the two headlights (left and right), pin 12 of the stepper motor controller for the LEFT-HAND headlight must be connected to earth. The SMC must be coded accordingly (either by the headlight manufacturer at the end of the production line or in the workshop after replacement).

Scheme 11

STEPPER MOTOR CONTROLLER BLOCK DIAGRAM LEGEND

Pin Assignment For The Stepper Motor Controller

PIN ASSIGNMENT FOR THE STEPPER MOTOR CONTROLLER

Preconditions for the stepper motor controller to work are correct coding and correct pin assignment as follows

1. Coding: Headlight-specific data for the adaptive headlights are coded in the stepper motor controllers.
2. Pin assignment: To differentiate between the installation location, pin 12 of the stepper motor controller (SMC) for the left-hand headlight must be connected to earth.

The stepper motor controller calculates the swivelling motion of the headlights for the adaptive headlights based on defined positions as follows

1. The stepper motor controller receives from the AHL control unit the position to which the headlight is to move (nominal value).
2. The stepper motor control recognises the current position of "its" headlight, i.e. the one to which it is assigned (actual value).
3. The stepper motor controller calculates the distance that the headlight must be moved (in steps). The stepper motor controller allows the stepper motor to turn as many steps as required until the headlights are in the correct position.

The defined positions, upon which the calculations are based, are checked each time the zero-position sensor is passed: the SMCs compare the calculated or driven-to zero to verify that the corresponding signal arrives from the zero-position sensor.

The output signal of the zero-position sensor is a level (depending on the degree of overlap of Hall sensor and sensor plate).

The output signal is either a high level signal or a low level signal. The level curve is illustrated in the following graphic

Scheme 12

OUTPUT SIGNAL LEGEND

Straight-Ahead Position

The headlights are aligned with the vehicle's longitudinal axis and shine straight ahead

This position is assigned the angle 0°.

The straight-ahead position is defined by two angles

1. Angle to the zero-position sensor
2. Angle to the mechanical reference point

The straight-ahead position is then calculated by the stepper motor controllers as follows

1. If the zero-position sensor is operational, the headlights are moved into the straight-ahead position from the position of the zero-position sensor.
2. If the zero-position sensor has failed, the headlights are moved into the straight-ahead position from the mechanical stop. (The headlights move into the straight-ahead position during the calibration sequence when terminal 15 is ON.)

Position Of The Zero-Position Sensor

The position of the zero-position sensor is set for each headlight and saved within the coding data of the stepper motor controller.

Mechanical Reference Point

There are two mechanical stops for each headlight. One of these mechanical stops is a reference point in case the zero-position sensor fails (it is determined during coding which of the two mechanical stops is the reference point).

Parked Position

The parked position is also defined as an angle to the straight-ahead position.

The parked position is important for the headlights' next calibration sequence

From the parked position, the headlights are run through a calibration sequence. The AHL control unit then "learns" the straight-ahead position of the headlights (calibration sequence when terminal 15 is ON in the pre-drive-check).

Detection Of Straight-Ahead Position In Operation

During operation, the swivel module moves to the straight-ahead position as follows

1. E46, E83, E63: zero-position sensor with level change: each time the flank is passed through (each time the level changes) in the defined direction, the nominal values are compared to the actual values. The number of steps required between the flank and the straight-ahead position is defined. If the swivel module has seized or become obstructed, there will be more steps to the level change than calculated. The stepper motor controllers take this difference into account ("lost steps" = steps moved by the stepper motor WITHOUT a corresponding change in the position of the swivel module). If the step losses (= "lost steps") exceed a permissible range, the level change is passed through repeatedly. The stepper motor controllers recognise the required number of steps. The swivel module is detected as having seized based on the number of steps completed (the reference values and actual values are then recalibrated by repeated swivelling of the headlight). The stepper motor controller also detects whether the swivel module is obstructed. If the swivel module is obstructed, the stepper motor controller attempts to move the headlight into the straight-ahead position. If the headlight cannot be moved into the straight-ahead position, the stepper motor controller switches off the headlight (switch-off conditions: sleep mode and restart detected; the fog lights are switched on as emergency lighting).
2. If the zero-position sensor is defective, the headlight is moved into the straight-ahead position based on the coded replacement values (from the mechanical reference point).

Swivelling Ranges

The swivel motors are controlled in a forwards and reverse direction from the straight-ahead position as follows

For example, the right-hand headlight has the following swivelling ranges

1. To the right as far as the coded end stop of the swivelling range: Swivelling angle 15° (from the straight-ahead position)
2. To the left as far as the coded end stop of the swivelling range: Swivelling angle 7° (from the straight-ahead position).

The stepper motor controller (SMC) sends the coded end stop of the swivelling range to the AHL control unit. The AHL control unit only outputs values that correspond to the coded end stop of the swivelling range.

E46 LSZ Control Unit

The LSZ control unit is the control unit for the light switch cluster.

Since the model year program in September 2001, the light switch cluster of the E46 has been overhauled as follows

1. Pulse-width modulated power supply for the vehicle lighting: The voltage for the vehicle lighting is output as a pulse-width modulated signal. The voltage has a fixed frequency of 80 Hz. This prevents lighting fluctuations when consumers with a high current draw are switched on.
2. Separate outputs on the light switch cluster (LSZ) for the tail lights, brake lights, rear fog lights and bi-xenon lights
3. Additional LSZ input for future dual-stage brake light (brake force display): There is an additional input in preparation for the dual-stage brake light (the brightness of the dual-stage brake lights is controlled as a function of the amount of braking force being used to decelerate the vehicle)

Scheme 13

LSZ CONTROL UNIT SCHEMATIC LEGEND

The LSZ control unit is installed behind the instrument panel, directly behind the light switch.

The range of functions of the light switch cluster includes the following tasks

1. Control and monitoring of the headlights and lamps on the exterior of the vehicle
2. Control and monitoring of the direction indicating and hazard warning flasher function
3. Dimmer for the instrument and locating lighting (terminal 58g) and the function and locating lighting for the hazard-warning switch
4. Evaluation of messages from the rain-light sensor for the automatic driving lights control and for the adaptive headlights
5. Communication with the trailer module, if fitted
6. Control of the green indicator lamp for the adaptive headlights
7. Data exchange via the K bus (see below for detailed description)
8. Data management for diagnostics and monitoring (see below for detailed description)
9. With option 522 "bi-xenon dipped/main beam headlights", the light switch cluster evaluates faults in the bi-xenon headlights.

Control And Monitoring Of The Headlights And Bulbs

All lighting loads are actuated and individually diagnosed via the light switch cluster.

1. Output limitation: If the on-board supply voltage exceeds a coded value, the lights are dimmed to increase the service life of the bulbs. A separate value is coded for each type of bulb (rear lights, brake lights, etc.). These values are coded during assembly, at the end of the production line.
2. Reduced ON current: The light switch cluster switches on the individual lights one at a time to prevent the vehicle electrical system from being overloaded unnecessarily by voltage peaks and high currents produced when the lights are switched on.
3. Prevents light intensity fluctuations: Valvetronic creates short load peaks resulting in voltage dips in the vehicle electrical system. These voltage dips can cause fluctuations in the intensity of the vehicle lighting. Corresponding parameters are stored in the light switch cluster to prevent visible light intensity fluctuations as much as possible.
4. Cold monitoring: For cold monitoring, the lights are switched on briefly without the bulbs glowing (thermal inertia of bulb elements). LEDs and D2-S bulbs (= xenon lights) are not cold-monitored (LEDs respond too quickly; D2-S bulbs must never be actuated by voltage pulses). Cold monitoring takes place when terminal 15 is switched ON. This pre-drive-check indicates the condition of the lights before the start of a journey (Check Control car symbol). Cold monitoring detects either "light available" or "open circuit". The cold current is a multiple of the rated current.
5. Hot monitoring: The rated current of bulb when it is switched on is monitored via the status output of the lamp driver. Within 2 seconds, a defective bulb can be recognised (frequency counters count the frequency of a recognised defect; the defect is reported when a certain number is reached). When the ignition is switched off, all frequency counters are reset to zero to prevent a bulb that has already been replaced from being reported as being defective again.

Data Exchange Via The K Bus

The light switch cluster receives the following messages via the K bus

1. Terminal R, signals from the basic module (GM or the ignition starter switch)
2. Parking lights
3. Dipped beam headlights
4. Front fog lights
5. Rear fog light
6. Ride-height sensors

The signals from the ride-height sensors are sent directly to the AHL control unit on vehicles with "adaptive headlights" option 524.

Data Management For Diagnostics And Monitoring

The light switch cluster stores data relevant to diagnostics

1. Stored fault codes
2. Bi-xenon diagnostics: In the event of a fault developing, the xenon control unit will issue a fault signal: residual current of approximately 20 mA, superimposed on a square-wave signal. If the light switch cluster receives the prompt through the K bus to initiate bi-xenon diagnostics, the light switch cluster switches over its internal driver output. A fault is only accepted as valid after being repeated 3 times.

E46 - Bi-Xenon Headlights

The bi-xenon headlights are a further development of the xenon headlights. With bi-xenon headlights, the xenon light can be directed up for the main beam headlights.

The bi-xenon headlights include the following components

1. Xenon-headlight control unit
2. Ignitor and D2-S bulb
3. Mechanical screen in front of the D2-S bulb for redirecting the dipped beam headlights when the main beam headlights are switched on (with a lifting magnet).
4. Return spring for mechanical screen

Scheme 14

The following bulb designations are available for bi-xenon headlights

1. D2-S bulb: bulb and ignitor are two components
2. D2-R bulb (for MINI and Rover L30); bulb and ignitor are two components
3. D2-S bulb: bulb and ignitor are part of ONE component (scheduled for introduction as of the E87)
4. D1-R bulb currently not in

When the dipped beam headlights are switched on, the mechanical screen is positioned vertically in front of the D2-S bulb (as illustrated). The beam of the xenon headlight is thus dipped.

When the main beam headlights are switched on, the mechanical screen in front of the D2-S bulb is moved from the vertical to the horizontal (folded forwards in the direction of travel).

This redirects the beam of the xenon headlight to main beam headlights. The rays of lights are able to shine uninterrupted to the front and to make use of the complete area of the reflector and the lens.

The mechanical screen in front of the D2-S bulb is controlled by the light switch cluster. If the light switch cluster is not able to actuate the lifting magnet for the mechanical screen, the screen is pulled back to the vertical position by the return spring.

E46 - Headlights

The dipped beam headlights may be halogen bulbs or D2-S bulbs (vehicles with "bi-xenon dipped/main beam headlights" option 522).

The main beam headlights are halogen bulbs.

The basic version consists of double circular headlights with halogen bulbs.

There is no automatic headlight-range adjustment on vehicles with double circular headlights and halogen bulbs.

The headlight range of the dipped beam is set manually using a thumbwheel on the light switch cluster.

Note. No manual headlight-range adjustment in USA Automatic headlight-range adjustment is a legal requirement in the USA.

The following options are available

1. European version: bi-xenon headlights with automatic headlight-range adjustment
2. In Europe and the USA: bi-xenon headlights with adaptive headlights (including automatic headlight-range adjustment)

The headlights on vehicles with "bi-xenon dipped/main beam headlights" option 522 consist of a double circular headlight with bi-xenon light and halogen bulb (in the main beam headlight only).

Scheme 15

Side Lights

Double circular headlight with halogen bulbs: each of the two reflectors is illuminated with light from one of the bulbs.

Side lights Double circular headlight with halogen bulbs: each of the two reflectors is illuminated with light from one of the bulbs. The reflector for the main beam headlights has side light rings. The light is fed into the side light rings by small reflectors (improved contrast).

Dipped Beam Headlights

1. Double circular headlight with halogen bulbs: the free-form reflector is fed by a bright H7 bulb. The free-form reflector ensures even distribution of light onto the road even in the case of headlights with halogen bulbs. A free-form reflector consists of individual, non-symmetrical surfaces in free-form design. This means that the beam is reflected onto the road as efficiently as possible. The driver's field of vision is illuminated in the best possible way. Reflectors used to be parabolic in shape.
2. Option 522 "Bi-xenon dipped/main beam headlights": an ellipsoid reflector, a 70mm lens and a state-of-the-art xenon bulb generate light of the normal intensity.

Main beam headlights

1. Double circular headlight with halogen bulbs: the H7 bulb and the reflector in the main beam headlight are matched to the dipped beam. This makes for efficient distribution of the entire beam onto the road and maximises the headlight range.
2. Option 522 "Bi-xenon dipped/main beam headlights": the D2-S bulb is used for both dipped and main beam headlights. To produce the main beam, a screen in the reflector for the bi-xenon headlight is folded back in front of the D2-S bulb. This increases the intensity of light from the bi-xenon headlight. In addition to this main beam from the bi-xenon headlight, the H7 bulb in the main beam headlight is also switched on.

US National Version

US models have the following features

1. Side marker lights
2. Main beam headlights by redirecting the bi-xenon headlights

Side Marker Lights On US Models

The side marker light is generated by the dimmed turn signals.

Main Beam By Redirecting The Bi-Xenon Headlights

In the USA, the main beam is produced by redirecting the bi-xenon headlights.

On US models, halogen bulbs are only used for the headlight flasher.

E46 - Adaptive Headlights (AHL), Diagnostics

Please note the following when performing diagnostics on the adaptive headlights

1. Switch-on conditions for the indicator lamp
2. Fault reported by customer: "Large sweep and then nothing".
3. Fault reported by customer: "No adaptive headlights at (e.g.) 80 km/h"
4. AHL control unit diagnostic mode
5. List of malfunctions for adaptive headlights
6. Diagnostics on bi-xenon lights

Indicator Lamp Flashes

The indicator lamp on the left of the light switch always flashes if a fault is detected in the system.

The indicator lamp also flashes if the bi-xenon headlights are defective and the adaptive headlights are deactivated for this reason.

The light switch cluster sends the message "Dipped beam headlights on" to the AHL control unit.

The message "Dipped beam headlights on" is generated separately for each bi-xenon headlight unit.

If one of the D2-S bulbs fails, the turning movement of the adaptive headlight function is deactivated.

Fault Reported By Customer: "Large Sweep And Then Nothing"

If terminal 15 is switched ON and the headlights move through a large sweep and then remain in the straight-ahead position, the signal from the zero-position sensor is not being received.

If the zero-position sensor fails, the position of the headlights is determined via a mechanical reference point as follows: The swivel module moves as far as the permitted mechanical end stop (= "large sweep") and then into the straight-ahead position. The turning movement of the adaptive headlights is then deactivated (= "and then nothing").

Fault Reported By Customer: "No Adaptive Headlights At (E.g.) 80 km/h"

If the adaptive headlights fail at speeds over 50 km/h, the signal from the yaw rate sensor is not being received. A fault memory entry must be present in the DSC control unit.

The indicator lamp must NOT be flashing.

The indicator lamp only flashes if there are faults in the adaptive headlight system. The yaw rate sensor is part of the DSC. This means that the indicator lamp will not indicate a fault in the yaw rate sensor.

AHL Control Unit Diagnostic Mode

For the following diagnostic operations, the AHL control unit must be set to diagnostic mode

1. Reading off relevant bus signals at a standstill shows whether or not the following signals are present: Road speed Yaw rate Steering angle
2. Check whether messages are received by the AHL control unit: Check AHL control unit inputs Check whether the AHL control unit is receiving any valid signals via the K CAN
3. Check whether switch-on conditions for the adaptive headlights are satisfied: Rain-light sensor status Light switch status

Faults are stored as follows

1. Faults in the stepper motors etc. are fed to the AHL control unit by the stepper motor controllers (SMCs) and stored in the AHL control unit.
2. The AHL control unit reports these faults in response to the status request (e.g. "communication with left-hand headlight failed").
3. Missing bus signals and missing signals from components are stored in the AHL control unit.

List Of Malfunctions For Adaptive Headlights

LIST OF MALFUNCTIONS FOR ADAPTIVE HEADLIGHTS

Diagnostics On Bi-Xenon Headlights

The light switch cluster (LSZ) checks whether or not current flows to the D2-S bulb of the bi-xenon headlights when the dipped beam headlights are switched on. If no current flows, the LSZ detects a fault and stores a fault message.

See also:
• E46 SYSTEM OVERVIEW OF ADAPTIVE HEADLIGHTS
• E46 LIGHT SWITCH ON THE LIGHT SWITCH CLUSTER
• E46 - DIRECTION INDICATOR/MAIN BEAM SWITCH
• E46 RIDE-HEIGHT SENSORS
• E46, E63, E64, E83, E90 - ZERO-POSITION SENSOR
• E46 - RAIN-LIGHT SENSOR
• E46 - AHL CONTROL UNIT FOR ADAPTIVE HEADLIGHTS
• E46 STEPPER MOTOR CONTROLLERS
• E46 LSZ CONTROL UNIT
• E46 - BI-XENON HEADLIGHTS
• E46 - HEADLIGHTS
• E46 - ADAPTIVE HEADLIGHTS (AHL), DIAGNOSTICS