Normal Operation
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The wheel speed sensor and sensor ring generates a square wave signal to the anti-lock brake system (ABS) module that is proportional to the wheel speed. The ABS module compares the wheel speed inputs from all the wheel speed sensors to determine an impending wheel lockup. Incorrect tire size can set these DTCs as well.