Switch Center, Steering Column, Supply

Steering Column Switch Center (SZL) And Multifunction Steering Wheel (MFL)

The functions of the steering column control center can be subdivided into three main blocks:
- Steering column switch center as satellite with connection to the BYTEFLIGHT bus
- Steering column switch center as switching center for the control functions at the steering column:
- Steering column setting via the button on the side of the steering column
- Steering wheel heating (not RR01) -> via the button on the left-hand side of the steering column

- Steering column switch center as steering-angle sensor.

The multifunction steering wheel provides the means by which the driver can easily and ergonomically perform the following functions:
- audio, telephone, Steptronic (not RR01), fanfare horn and a definable button -> via the function buttons of the multifunction steering wheel
- direction indicators / high beam headlights, gear selector lever, windshield wiper, cruise control (FGR), -> via the 4 control levers on the steering column

Brief description of components
The multifunction steering wheel consists of
- 4 steering-column levers: All steering-column levers are one-touch levers and do not lock in the operated position
- Fanfare horn
- 4 Steptronic buttons (not RR01),
- 2 blocks with function buttons
- Airbag system
- Heating coil and temperature sensor in the steering wheel rim (not RR01).

Located below the multifunction steering wheel are
- a button for the steering column setting
- a button for the steering wheel heating (not RR01)
- the control module of the steering column control center with integral steering angle sensor

The electronic control system for the steering column control center and the multifunction steering wheel is divided into two electronic modules:
- Steering column electronics (= steering column switch center)
- Steering wheel electronics.

Signal transmission from the steering wheel module to the steering column module is effected by means of a coil-spring conductor.

Steering column stalk, top left: Turn indicator-low beam switch
The turn indicator-low beam switch consists of
- a steering-column lever
- two one-touch buttons.

The turn signal/dip switch also incorporates two axial touch switches .
- The top button activates the Info display on the right of instrument cluster below the tachometer.
- The bottom button activates the Info display on the left of instrument cluster below the speedometer.

Transfer concept: steering column stalks and axial touch buttons have differing signal transmission routes:

Steering column stalk signal transmission route: When the driver operates the steering column lever, a message is sent to the light module. Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus K-CAN SYSTEM -> light module.

For safety reasons, there is an additional serial cable from the steering column switch center to the light module. An analogue coded signal is applied to that cable and is analyzed by the light module. Each switch position is allocated a voltage range. The serial cable enables transmission of all positions of the turn signal/dip switch in the event of a bus fault, though with some limitations to the possible functions:
- High beam and headlamp flasher only function if the steering column stalk is held in position.
- The direction indicators only function while the steering column stalk is held in position, no continuous flashing, no automatic reset
- No hazard-warning lights in the event of a crash and when arming the antitheft alarm.

Touch button signal transmission path: When the driver operates one of the axial touch buttons, a message is sent to the instrument cluster.

Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus K-CAN SYSTEM -> instrument cluster.

Steering-column lever, bottom left: vehicle speed control
The lever for the cruise-control system consists of
- a steering-column lever
- a one-touch button
- a knurled wheel (not RR01).

Speed marks of required speeds: the steering-column lever for cruise control can also be used to select required speeds. Required speeds are e.g. frequent speeds used, such as 30 km/h, 50 km/h, 60 km/h. Speed marks can be set and stored for these required speeds.

The preset cruise control speeds are car & key memory functions, i.e. they can be set and stored individually for each driver.

Transfer concept: When the driver operates the steering-column lever or the axial one-touch button, a message is sent to the digital engine electronics.

Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus PT-CAN -> digital engine electronics.

Transfer concept: When the driver operates the knurled wheel (not RR01), a message is sent to the active cruise control (ACC) control module.

Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus PT-CAN -> active cruise control (ACC).

Steering-column lever, top right: selector lever
The gear selector lever is used for fully electronic selection of the gear positions R - N - D and P (reverse gear-neutral position-drive-park position). The gear selector lever consists of
- a steering-column lever
- a one-touch button

The desired drive position is registered by seven Hall sensors. The Hall sensor are configured in such a way that if an individual Hall sensor fails the operability of the gear selector lever is retained.

Transfer concept: When the driver operates the steering-column lever or the axial one-touch button, a message is sent to the Electronic Transmission Control.

Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus PT-CAN -> Electronic Transmission Control.

For safety reasons, there is a serial cable from the steering column switch center to the electronic transmission control. The same messages are transferred on this cable as across the data buses.

Electronic parking lock: with electronic transmission control, the steering column lock can be eliminated as an antitheft measure: the electronic parking lock replaces the steering column lock.

Electronic parking lock "emergency" release: in an emergency, the electronic parking lock be unlocked mechanically:
- Remove the cover in the driver's side footwell near the left A pillar.
- Unlock the electronic parking lock manually.

Steering column stalk, bottom right: Wiper switch
The wiper switch consists of:
- a steering-column lever
- a one-touch button
- a knurled wheel (not RR01).

At "ignition off", the wiper and the rain/light sensor are switched off.

Transfer concept: When the driver operates the steering column lever for the windshield wipers, a message is sent to the wiper module.

When the driver operates the axial button or the knurled wheel (not RR01),
- on a vehicle without rain/light sensor, a message is sent to the wiper module.
- on a vehicle with rain/light sensor, a message is sent to the rain/light sensor control module.

Signal path: from steering column switch center -> data bus BYTEFLIGHT -> Safety and Information Module -> data bus BYTEFLIGHT -> Central gateway module -> data bus K-CAN SYSTEM-> wiper module or rain/light sensor.

Steptronic buttons (not RR01)
Operating the Steptronic button causes the electronic transmission control to shift gear upwards or downwards.

The Steptronic buttons are redundant for safety reasons, one each to the left and right on the multifunction steering wheel.

The Steptronic buttons are only enabled when the S/M key (S = Sport program, M = Manual shift program) on the right of the multifunction steering wheel has been switched to Manual: an M is displayed in the program display of the instrument cluster (display area between speedometer and tachometer). Depending on the gear selection, M1 to M6 appears for the current gear.
- The Steptronic buttons (+) in the upper area of the multifunction steering wheel are used for upshifts.
- The Steptronic buttons (-) in the lower area of the multifunction steering wheel are used for downshifts.

The Steptronic buttons are Hall sensors.

For safety reasons, there is a redundant serial cable from the steering column switch center to the electronic transmission control.

Function button block on the left and right of the multifunction steering wheel
The function buttons enable selection of
- Voice input
- Search
- Audio functions (radio, telephone, etc.)

Steering wheel adjuster button
The steering wheel is adjusted by means of the button on the side of the steering column trim.
- Semi-electrical steering wheel adjustment (not RR01): press steering wheel adjustment button. An electric motor releases the steering column lock for five seconds.

Within that period, the driver can adjust the position of the steering wheel manually as required.

After five seconds, the steering column is automatically locked in position again.

If the period of five seconds is too long for the driver, the steering column can be locked immediately by pressing the button again.

- Fully electric steering column setting: the steering wheel position is adjusted electrically by means of a button. The adjuster button has four possible directions of movement. These enable the steering wheel to be moved up, down, forwards or backwards.

The choice of steering wheel position is a Car&Key Memory function. It is memorized together with the driver's seat position.

When the ignition is switched off and the door contact signals "open", the steering wheel is moved to its highest and most forward position so as to make getting in and out of the car easier.

Fanfare horns
The fanfare horns serve both as a warning signal and as redundant-system audible alarms of the vehicle.

The directly read horn switch signal is sent as a valid status via the steering wheel module and the coil spring conductor to the steering column module (control module of the steering column control center). The steering column module can control the high-tone and low-tone horns separately. The power consumption for each horn is approx. 5 A.

Steering wheel heating (not RR01)
The steering wheel heating system consists of
- a button on the left of the steering column for switching the steering wheel heater on and off
- a function indicator in the steering wheel heater switch which lights up when the steering wheel heater is on.
- the heater coil in the steering wheel rim which heats up the steering wheel
- a temperature sensor in the steering wheel rim which sends the temperature signal back to the steering column module.

The steering column control center activates the heater coil as required in order to ensure even heating of the steering wheel.

Service functions

Notes on safety
In all cases, only perform work on the fuel pump with the ignition off!

All work on the airbags must be carried out with the battery disconnected!

Connect and disconnect all BYTEFLIGHT control modules, sensors and generators only with the battery disconnected!

If a fiber-optic cable on the BYTEFLIGHT bus has to be repaired, it must be borne in mind that there may only be one join between the Safety and Information Module and a satellite. For this reason, no repairs may be performed on the fiber-optic cable between the Safety and Information Module and the the door satellites, as there is already a join with the door connector. In the case of a defect, the fiber-optic cable must be replaced!