Wheel Speed Sensor: Description and Operation

PURPOSE
At each wheel hub there is a tone wheel and an inductive sensor, which supplies wheel speed information to the ABS Control Module (ABSCM).

FUNCTION
The sensor is comprised of a magnet and a pole piece surrounded by a coil. When the tone wheel rotates adjacent to the sensor pole piece, an alternating current signal is generated in the coil with a frequency proportional to wheel speed. A special integrated circuit in the ABSCM translates the generated AC signal to a square wave. This square wave is used by the microprocessor to operate the ABS.