Steering Wheel Angle Sensor (657): Function: Notes

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.

Fig 1: Identifying Steering Wheel Angle Sensor Comprises Ring Gear

Courtesy of SAAB-SCANIA OF AMERICA, INC.

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.

Fig 2: Identifying Steering Wheel Angle Sensor

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 3: Steering Wheel Angle Sensor - Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The steering wheel angle sensor contains a microprocessor with self-diagnosis function. The microprocessor sends information over the P-bus.

• Calibration signal
• Steering wheel angle
• Information on status
• DTC