Wheel Speed Sensor: Description and Operation

Fig. 7 Wheel Sensor Assembly (righthand Side Shown, Lefthand Side Similar). 1989 Continental:

Fig. 8 Wheel Sensor Assembly. Cougar & Thunderbird:

Fig. 9 Wheel Sensor Assembly. Mark VII:

This system, Figs. 7 through 9, uses four sets of variable reluctance sensors and toothed speed indicator rings to determine the rotational speed of each wheel. The sensors operate on magnetic induction principle. For example, as the teeth on the speed indicator ring rotate past the stationary sensor, a signal proportional to the speed of the rotation is generated and transmitted to the electronic control unit (ECU) through a coaxial cable.
The front sensors are attached to the suspension knuckles and the speed indicator rings are pressed onto the outer constant velocity joints. The rear sensors are attached to the rear caliper anchor plate and the speed indicator rings are pressed onto the rear wheel hub assemblies. The sensors and the speed indicator rings are serviced individually.