The steering angle is recorded in 2.5° steps by photoelectric barriers. The signal recording system is designed for a steering angle of 720° (4 steering wheel revolutions).
In the center position of the steering wheel the 8 apertures assume a defined position relative to the 9 light-emitting diodes. This center position is recorded by the computer in the steering angle sensor.
When the steering wheel is turned the position of the apertures relative to the light-emitting diodes changes (light/dark). This produces a quite specific signal pattern due to the different length apertures and aperture spacings. Angle values are calculated with the aid of the signal patterns and converted into serial information for the control module connected.
The voltage is supplied to the steering angle sensor (N49) via terminal 30 so that the steering angle can also be recorded after «ignition OFF».
The steering angle sensor (N49) must be re-initialized after the voltage is interrupted (terminal 30). This is achieved by:
Turning the steering wheel from stop to stop or
Driving straight ahead at a speed > approx. 20 km/h over a distance of > approx. 50 m.