The anti-lock brake system (ABS) modulates brake pressure on each wheel independently to maintain vehicle stability during braking. The ABS continually monitors the rotational velocity of each wheel anytime the ignition switch is in the run position and determines if a tire is skidding when the brakes are applied. Only then does the ABS intervene to modulate the brake pressure to the skidding wheel. The modulation continues until the wheel rotates freely. The brake pressure is then restored and the modulate/restore cycle is repeated whenever skidding is detected. This cycle occurs at a rate of several times per second.
The ABS module is capable of detecting the following system conditions: hydraulic valve failure, wheel speed sensor failure, ABS power relay short circuit, interconnect failures to the ABS sensors, power and ground to the ABS module and over/under voltage conditions.