Brief Description Of Components

The sensors incorporated into the Active Front Steering system are:

• Motor-position sensor 

  The motor-position sensor registers the rotor position of the electric servomotor. The rotor position is communicated to the control unit for Active Steering (AL control unit).

  The 3rd generation Active Steering includes a digital motor-position sensor.

• Cumulative steering angle sensor and steering angle sensor 

  The cumulative steering angle sensor captures the steering angle that the Active Steering produces at the steering box.

  As far as its function is concerned, the cumulative steering angle sensor corresponds to the steering angle sensor in a conventional steering system. The steering angle sensor in the steering column switch cluster registers the angle to which the driver turns the steering wheel. Both signals are needed by the control unit for Active Steering (AL control unit).

  • > From E70 (other model series to follow)

  The cumulative steering angle sensor on the X5 is discontinued. Active Steering computes a "virtual" cumulative steering angle. The virtual cumulative steering angle is derived from the following signals:

  • Steering angle sensor signal
  • Motor-position sensor signal

  The steering angle sensor on the BMW 1 and 3-Series is an optical sensor.

  From 09/2005, the BMW 5 and 6-Series also have an optical steering angle sensor.

• DSC sensor 
  • >  E60, E61, E63, E64 up to 09/2005:

    2 DSC sensors transmit redundant signals capturing the rate of yaw (rotation about the vertical axis) and lateral acceleration to the AL control unit via the chassis CAN (F-CAN).

  • >  E70, E81, E87, E90, E91, E93, E93

    Only 1 DSC sensor is needed for the Active Steering. This DSC sensor transmits redundant signals capturing the rate of yaw and the lateral acceleration.

  • > E60, E61, E63, E64 from 09/2005

    Only 1 DSC sensor is needed for the Active Steering.

    This DSC sensor transmits redundant signals capturing the rate of yaw and the lateral acceleration.

The control units networked for the purposes of AFS are as follows:

• AL: Active Steering control unit 

  The AL control unit computes the nominal values for the electric servomotor of the planetary gearbox with override function.

• SZL: Steering Column Switch 

  The Steering Column Switch provides the steering angle.

• SGM: Safety and gateway module 
  • > E60, E61, E63, E64 up to 09/2005

  The safety and gateway module (SGM) drives the ECO valve in the power-steering pump and the Servotronic valve.

  Moreover, the SGM forms the interface between the PT-CAN and the K-CAN (signals for instrument cluster).

• KGM: Body gateway module 
  • > E60, E61, E63, E64 from 09/2005

  The body gateway module (KGM) forms the interface between the PT-CAN and the K-CAN (signals for instrument cluster).

  With option 216 "Servotronic", the KGM actuates the Servotronic valve.

• JBE: Junction box electronics 
  • > E70, E81, E87, E90, E91, E92, E93

  The junction box electronics (JBE) forms the interface between the PT-CAN and the K-CAN (signals for instrument cluster).

  Moreover, the AL control unit receives its power supply from the distributor in the junction box.

• DSC: Dynamic Stability Control 

  The DSC control unit and the AL control unit are interconnected by the F-CAN (chassis CAN). The signals supplied by the DSC control unit include the road speed signal.

• DME or DDE: digital engine electronics or digital diesel electronics 

  The engine control sends the signal indicating that the engine is running to the AL control unit via the PT-CAN bus. The AL control unit notifies the engine control of the approximate drive torque of the power-steering pump.

• CAS: Car access system 

  The vehicle is authenticated by the AL control unit and the CAS control unit via the K-CAN / PT-CAN (vehicle identification numbers compared).

  Moreover, the CAS control unit transmits the wake-up signal for the PT-CAN.

The following actuators are actuated by the Active Steering:

• Planetary gearbox with override function and electric servomotor 

  The planetary gearbox with override function uses the electric servomotor to generate the resulting cumulative steering angle at the front wheels.

• Hydraulic steering with Servotronic valve 

  The conventional hydraulic steering provides the power-steering assistance.

  "Servotronic" (= speed-dependent power-assisted steering) is part of the Active Steering option.

• ECO valve in the power-steering pump 

  A vehicle fitted with the "Active Steering" option has a controlled-output power-steering pump.

• Warning light and Check Control 

  The dedicated-function warning light in the instrument cluster lights up to indicate a fault in the Active Steering.

  At the same time a Check-Control message is shown in the LCD display. The text for the Check-Control message can be called up in the Central Information Display (CID).

The steering-column adjustment consists of the following components:

• Switch for steering-column adjustment 

  This switch enables the driver to adjust the tilt and reach setting of the steering column. The switch for steering-column adjustment is on the left-hand side of the steering column.

• Steering-column adjustment drive unit 

  Two motors are built into the drive unit. 1 motor drives the tilt and reach adjustment of the steering column. The second motor changes the direction of adjustment via the adjustment gears.

  The adjustment movement and position recognition for both tilt and reach adjustment are recorded in the drive unit for the steering-column memory. There are 2 Hall sensors and 2 magnetic rings (16-pin) integrated in the drive unit.

• Steering column switch cluster 

  The switch for steering-column adjustment sends its signal to the steering column switch cluster (SZL). The steering column switch cluster forwards this signal to the centre console switch cluster (SZM).

  • >up to 09/2005

  Signal path: Switch for steering-column adjustment --> Steering column switch cluster (SZL) --> byteflight  --> Safety and gateway module (SGM) --> K-CAN --> Centre console switch cluster (SZM).

  • >from 09/2005

  Signal path: Switch for steering-column adjustment --> Steering column switch cluster (SZL) --> Body gateway module (KGM) --> K-CAN --> Centre console switch cluster (SZM).

• Centre console switch cluster 

  The centre console switch cluster (SZM) actuates the steering-column adjustment. The centre console switch cluster also stores the positions for the steering-column memory.

• Door contact in the driver's door 

The centre console switch cluster needs the signal from the door contact. The signal for easy entry and exit is used in conjunction with the terminal status.

• >up to 09/2005

Signal path: Driver's door contact switch --> Driver's door module (TMFA) --> byteflight  --> Safety and gateway module (SGM) --> K-CAN --> Centre console switch cluster (SZM).

• > from 09/2005

Signal path: Driver's door contact switch --> Body gateway module (KGM) --> K-CAN --> Centre console switch cluster (SZM).