Steering wheel angle sensor (657)
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Steering wheel angle sensor (657)
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The steering wheel angle sensor is located on the steering column between the steering wheel and the intermediate shaft. The sensor senses the angle of the steering wheel and is connected to the P-bus. The sensor provides the ESP control module with information on steering wheel angle.
The steering wheel angle sensor comprises a ring gear (1) mounted on the steering column shaft. Two gears with different numbers of teeth (2a has 28 teeth and 2b 26 teeth) engage this ring gear. Each gear has a permanent magnet (3a and 3b) and sensor, the resistance of which depends on the magnetic field.
Since the two gears 2a and 2b have different numbers of teeth, the relative positions of the permanent magnets will be unique for each steering wheel angle. Accordingly, the position of the steering wheel can be transmitted on the P-bus. This information is used by the ESP control module.
The steering wheel angle sensor contains a microprocessor with self-diagnosis function. The microprocessor sends information over the P-bus.
Bus messages
The steering wheel angle sensor sends the following information over the P-bus. This information is used by the ESP control module.
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Sends
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Value
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Description
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Diagnostics
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OK / NOK
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Self diagnosis
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Steering wheel angle
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±530°
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Steering wheel position
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The steering wheel angle sensor receives the following information on the P-bus. This information is sent by the ESP control module.
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Sends
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Value
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Description
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Calibrated
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Yes / No
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See
Calibration
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In order for the microprocessor to know the straight-ahead position (0-position), the sensor must first be calibrated. When calibrating, the steering wheel angle sensor receives information that the steering wheel and the road wheels are in 0 position (straight-ahead).
Calibration must be performed after working on the front assembly or after changing the steering wheel angle sensor. This is done as described in
Calibration of steering wheel angle sensor
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If the correction value is 15°, the system is disabled and the
TCS OFF/ESP OFF indicator lamp
comes on.
DTC generated in ESP control module.
