Wheel Speed Sensor: Description and Operation

CAUTION: The tone wheels used on this vehicle equipped with the Teves Mark 20 Antilock Brake System are different then the tone wheels used on past models of this vehicle equipped with antilock brakes. Reduced braking performance will result if this part is used on earlier model vehicles and an accident could result. Do not use on pre-1998 model year vehicles.

Front Wheel Speed Sensor:

Rear Wheel Speed Sensor With Disc Brakes:

One Wheel Speed Sensor (WSS) is located at each wheel, and sends a small AC signal to the control module Controller Antilock Brake (CAB). This signal is generated by magnetic induction created when a toothed sensor ring (tone wheel) passes the stationary magnetic Wheel Speed Sensor. The CAB converts the AC signal generated at each wheel into a digital signal. If a wheel locking tendency is detected by the CAB, it will then modulate hydraulic pressure via the Hydraulic Control Unit (HCU) to prevent the wheel(s) from locking.

The front Wheel Speed Sensor is attached to a boss in the steering knuckle. The tone wheel is part of the outboard constant velocity joint. The rear Wheel Speed Sensor on rear disc brake applications is mounted to the rear disc brake adapter and the rear tone wheel is also an integral part of the rear wheel hub and bearing assembly. The speed sensor air gap on both applications is NOT adjustable.

The four Wheel Speed Sensors are serviced individually. The front Tone Wheels are serviced as an assembly with the outboard constant velocity joint. The rear Tone Wheels are serviced as an assembly with the rear hub and bearing assembly.

Correct ABS system operation is dependent on accurate wheel speed signals. The vehicle's wheels and tires must all be the same size and type to generate accurate signals. Variations in wheel and tire size can produce inaccurate wheel speed signals.