Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The wheel speed sensor and sensor tone ring generate a square wave signal to the anti-lock brake system (ABS) module that is proportional to wheel speed. The ABS module compares wheel speed inputs from all wheel speed sensors to determine an impending wheel lockup.
Voltage and ground signals are supplied to the wheel speed sensors from the ABS module. A malfunctioning wheel speed sensor, damaged sensor tone ring or an open, short to ground or short to voltage in the wheel speed sensor wiring may cause one or more of the diagnostic trouble codes (DTCs) to set.
Incorrect and/or mismatched tires installed on the vehicle as well as low tire pressure in one or more tires may cause DTC C1222 to set.