Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The wheel speed sensor and sensor ring generate a square wave signal to the ABS module that is proportional to the wheel speed. The ABS module compares the wheel speed inputs from all of the wheel speed sensors to determine an impending wheel lockup.