The steering angle sensor measures the present angle of the steering wheel, the direction the steering wheel is actively being rotated and the angular rotational speed at which the steering wheel is being rotated.
The steering angle sensor is part of the steering column switch cluster (referred to as the SZL) located below the horn and airbag in the steering wheel. The SZL is a donut shaped assembly that includes the steering angle sensor, turn signal switch, cruise control, on board computer switch, wiper and washer switch, headlight beam switch and airbag and horn contact springs. The steering angle sensor switch is an optical device that makes measurements by using an optical sensor to read the marks on a disc that rotates in unison with the steering wheel.
The information supplied by the steering angle sensor is used by the dynamic steering control system, and if so equipped the active steering and active roll stabilization systems.
Upon initialization of the system the steering wheel is set so the wheels/tires point straight ahead and the steering wheel is in the centered neutral position. Then a calibration program is run to allow the computer to sync the optical sensor with the centered position. Because the E60 is so electrical system dependent, a weak battery or disconnected battery can generate a fault in the steering angle sensor (in addition to many other systems). In most cases after correcting the low voltage condition, turning the steering wheel all the way in one direction until lock and then back in the other direction until lock allows the steering angle sensor to reset itself and begin working again.
Another failure mode of the system is a plastic window through which the marks on the rotating wheel are read by the sensor. The window can become cloudy and the optical sensor can no longer read the marks on the wheel, causing a failure of the sensor system. Some DIY repairs have been successful cleaning this small plastic window, though disassembly and reassembly of the steering wheel is to say the least complicated.
Don't know what year your 525i is, but ran across this SIB for steering faults this evening.
Make / Models:
BMW / 5 SERIES
BMW / 5-SERIES
BMW / 6 SERIES
BMW / 7 SERIES
February 1, 2012
Service Bulletin Number:
NHTSA Item Number:
BMW: STEERING COLUMN SWITCH CENTER CONTAINS ONE OR MORE FAULTS: INTERNAL CONTROL, STEERING WHEEL LOCK RANGE EXCEEDED, WIPER ANGLE DEFECTIVE. VARIOUS CHECK CONTROL MESSAGES APPEAR WITH AIRBAG WARNING LAMP ILLUMINATED. *PE
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