The steering column switching centre (SZL) has a conventional structure. The steering column switching centre is connected to the attachments by cables. There is no optical signal transfer as on e.g. the BMW 3 Series.
The steering column switching centre has the following tasks:
If the vehicle is equipped with optional extra 210 ”Dynamic Stability Control”, the steering column switching centre is also connected to the chassis CAN (F-CAN).
On vehicles without DSC, the steering column switching centre has no steering-angle sensor.
The following components are described for the steering column switching centre (SZL):
The steering-column lever on the left of the steering column has the following functions:
The lines for the lighting are routed through the steering column switching centre. From the SZL, the lines lead to the footwell module (FRM), which activates the lighting.
The signal of the onboard computer button is sent on the PT-CAN to the instrument cluster.
The steering-column lever on the right of the steering column has the following functions:
The signals of the wipe-wash switch are sent by the steering column switching centre across the PT-CAN to the junction box electronics (JBE). The JBE activates the wipe-wash system.
The knurled wheel for manual headlight vertical aim control (3 positions) is on the left-hand side trim panel of the steering column.
Index |
Explanation |
Index |
Explanation |
|---|---|---|---|
1 |
Steering column switch cluster |
2 |
Knurled wheel for headlight vertical aim control |
The signal from the knurled wheel is routed through the steering column switching centre. The footwell module (FRM) activates the headlight vertical aim control.
The steering-angle sensor is in the steering column electronics of the steering column switching centre.
Index |
Explanation |
Index |
Explanation |
|---|---|---|---|
1 |
Steering column switch cluster (SZL) |
2 |
Steering angle sensor |
3 |
Wipe-wash switch |
4 |
Turn indicator / main-beam switch |
The steering-angle sensor picks up the following variables:
These variables are required e.g. by the dynamic stability control (DSC) or electromechanical power steering (EPS). The signals are sent from the SZL on the PT-CAN as well as the F-CAN.
The multifunction steering wheel is connected via cables and a K bus with the SZL.
The multifunction steering wheel has the following functions:
The cable from the switch for the horn is routed through the SZL. The signal is forwarded to the junction box electronics.
The cables for the driver's airbag run through the SZL. From the SZL, the cables lead to the multiple restraint system (MRS control unit).
Index |
Explanation |
Index |
Explanation |
|---|---|---|---|
1 |
Rocker switch on the left |
2 |
Horn |
3 |
Rocker switch on the right |
4 |
MFL button pad on the right |
5 |
Push-to-Talk button |
6 |
Telephone button |
7 |
MFL button pad, left |
|
|
With optional extra 205 ”Automatic gearbox”, the rocker switches are also integrated on the multifunction steering wheel.
The two rocker switches are identical in structure and switched in parallel.
Pulling one or both of the rocker switches shifts a gear upwards. Pressing one or both of the rocker switches shifts a gear downwards.
The following control units are involved in the functions of the SZL:
The footwell module (FRM) receives the signals of the turn indicator / main-beam switch. The FRM thus activates the exterior lighting, including the headlight vertical aim control.
The junction box electronics activate the two horns via a relay in the JBE. In addition, the JBE supplies the steering column switching centre with terminal 30.
The DSC requires the signals of the steering-angle sensor. These signals are sent on the F-CAN.
The electromechanical power steering (EPS) also uses the signals of the steering-angle sensor. The signals are sent on the PT-CAN.
In the case of a steering column switching centre without steering-angle sensor, the EPS calculates the steering angle from other measured variables.
The multiple restraint system activates the driver's airbag. To this end, the lines are routed through the steering column switching centre to the multifunction steering wheel.
The Electronic Gearbox Control (EGS) receives the signals of the rocker switches from the steering column switching centre. This enables the EGS to shift the gears of the automatic gearbox.
The instrument cluster receives the signals for activation of warning and indicator lamps on the body CAN.
The following system functions are described for the steering column switching centre:
The variants for the steering column switching centre (SZL) depend on the options fitted. The SZL is available without steering-angle sensor (basic version) and with steering-angle sensor with dynamic stability control (High equipment).
The following optional extras expand the variants:
The steering column switching centre can be connected to the following bus systems:
The K bus runs from the steering column switching centre to the right-hand MFL button pad. The left-hand MFL button pad is connected via the right-hand MFL button pad.
The buffer spring cassette transfers electrical signals inside the steering wheel and from the steering wheel.
The undervoltage detection and overvoltage detection range from 9 Volts to 16 Volts.
Outside of this range, no fault is stored in the fault code memory. Exceptions are fault code memory entries that refer directly to undervoltage or overvoltage.
The steering-angle sensor in the steering column switching centre can be calibrated for the following angular range: ± 15°.
The steering-angle sensor is fixed in the SZL due to its design.
A service function is available in the BMW diagnosis system for the steering-angle sensor adjustment.
Diagnosis for the multifunction steering wheel and cruise-control system is implemented in the SZL (fault code memory entries in the event of faults).
If the SZL receives no information from the multifunction steering wheel or cruise-control system (e.g. on starting up):
the messages on the PT-CAN are filled with ”Signal invalid”.
The steering column switching centre (SZL) cannot be coded.
In the event of replacement, the steering column switching centre is delivered programmed. The steering-angle sensor in the SZL must be calibrated after replacement.
The steering column switching centre is active under the following conditions:
No liability can be accepted for printing or other errors. Subject to changes of a technical nature