The anti-lock brake system is a computer operated hydraulic controlled system that rapidly applies the brakes on and off to make sure your brakes do not lock up and cause you to skid during a sudden stop or on slick surfaces. ABS Sensors help this system by providing the ABS Computer with signals of information on the wheel's rotational speed. The ABS sensor is also called the wheel speed sensor or ABS brake sensor. When one wheel speed is detected to be at a different speed than the others the powertrain control module (PCM) sends a signal to the Anti-locking brake control module that there is a problem and to activate the anti-locking brake system.