Wheel Speed Sensors and Tone Wheels

Front Wheel Speed Sensor:

Rear Wheel Speed Sensor (FWD):

Rear Wheel Speed Sensor (AWD):

DESCRIPTION
The front Wheel Speed Sensor (WSS) is attached to a boss in the steering knuckle. The front toothed sensor ring (tone wheel) is part of the driveshaft's outboard constant velocity joint. The rear wheel speed sensor is mounted through the rear axle, rear brake support plate and directly to the rear bearing. The rear toothed sensor ring (tone wheel) is an integral part of the rear wheel hub/bearing assembly. If damaged, the rear tone wheel can be replaced as an individual component of the rear hub/bearing assembly. The wheel speed sensor air gap is NOT adjustable.

OPERATION
One WSS is located at each front and rear wheel of the vehicle. The wheel speed sensor sends a small AC signal to the Controller Antilock Brake (CAB). This signal is generated by magnetic induction created when the 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.

NOTE: 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, which can cause false ABS cycles to occur.