Functional description, see BMW Technology:
TIS -> Document -> SI Technology -> Enter SBT number SBT number: 61 07 04 103
As calculation basis for the various functions of the DSC, the steering column switching centre (SZL) picks up the steering angle and steering-wheel turn information, among other things.
The steering angle indicates the angle position of the steering wheel. A steering angle of +/-180° is picked up. The steering-angle-sensor signal repeats itself every 360°. The steering-wheel turns are counted via these signal repetitions. The SZL is supplied permanently via terminal 30. This means that the steering wheel movements are also picked up with ignition OFF. After a power interruption, the neutral position of the steering wheel is retained. However, the steering-wheel turn is lost. A calculation model re-determines the current steering-wheel turn while the vehicle is being driven. If this operation has not been completed by the time a road speed of 25 kph has been reached, the DSC warning lamp is set. Other possibilities to determine the steering-wheel position after power interruption: Steering from limit position to limit position Running the service function ”Calibrate Steering Angle”
In order to perform its internal calculations, the steering angle sensor requires model-specific data which has to be loaded onto it by means of coding.
During calibration, the current steering-wheel position is stored permanently as the straight-ahead setting of the steering wheel in the SZL. For this reason, during calibration the front wheels and the steering wheel must be placed in an exact straight-ahead setting. In addition,the serial number of the SZL and the vehicle identification number are stored in the DSC (assignment of DSC to SZL and vehicle). After successful calibration, the fault code memory of the steering-angle sensor is automatically deleted.
Calibration must always be carried out after the following operations: