Grand Cherokee 2WD Limited V8-4.7L (2002)
Wheel Speed Sensor: Description and Operation
WHEEL SPEED SENSORS AND TONE WHEELS
One wheel speed sensor (WSS) is located at each wheel and sends a small DC voltage signal to the control module (CAB). The CAB sends 12 volts
down to the sensor. The sensor has an internal magneto resistance bridge that alters the voltage and amperage of the signal circuit. This voltage and
amperage is changed by magnetic induction when a toothed sensor ring (tone wheel) passes by a stationary magnetic sensor (wheel speed sensor). The
CAB measures the voltage and amperage of the DC signals for each wheel.
The front wheel sensor is attached to a boss in the steering knuckle. The tone wheel is an integral part of the front axle shaft. The rear speed sensor is
mounted in the caliper adapter plate (rear disc only) and the rear tone wheel is an integral part of the rear rotor hub. The wheel speed sensor air gap is
NOT adjustable. Because of internal circuitry, a resistance check of WJ wheel speed sensors will not determine correct or incorrect function.
Correct antilock system operation is dependent on wheel speed signals from the wheel speed sensors. The vehicle's wheels and tires should all be the
same size and type to generate accurate signals. In addition, the tires should be inflated to the recommended pressures for optimum system operation.
Variations in wheel and tire size or significant variations in inflation pressure can produce inaccurate wheel speed signals; however, the system will
continue to function when using the mini-spare.
When driven over rough road surfaces, the rear wheel speed sensor signals may be erratic and cause a false trouble code (drum brakes only).
