steering angle sensor main functions

The total steering angle output by the steering-angle sensor is composed of the following three values:
· Correction value of the steering-angle sensor, this correction value sets the zero-degree position of the steering wheel. The correction value is set and stored on calibration of the steering-angle sensor. The correction value results from the difference between the steering angle of the potentiometer and zero degrees.
· Current measured steering angle of the potentiometer
· Number of steering-wheel turns
So that the total steering wheel angle is available at all times, uninterrupted measurement of all steering wheel movements is required, also if the vehicle is at a standstill. In order to achieve this, the steering angle sensor is permanently supplied with power from Terminal 30.
This means that steering wheel movements at(ignition off) are also recorded. The correction value determined during calibration and the steering angle recorded by the potentiometers are still available after power interruptions, but not the number of steering-wheel turns. So that the steering-angle sensor remains able to operate after power interruptions, software has been integrated that uses the wheel speeds or an adjustment of the steering wheel from stop to stop to calculate the number of steering wheel turns.
If this does not work on moving off and reaching a speed of approx. 25 km/h, the DSC switches to passive and a fault is entered in the DSC control module. There is no fault entry in the steering angle sensor.
In order to further ensure the function, a comparative value is determined continuously both in the DSC and the EDC control modules to compensate for deviations in the zero position of the steering-angle sensor.
Deviations can result from inaccuracies during calibration, from wear or impacts with the curb.

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