ABS stands for Anti-lock Brake System which helps to improve vehicle steer-ability, Directional stability and optimal deceleration on severe braking and on varying types of road surfaces, by continuous monitoring of each wheel's speed and pressure control of brake line to avoid wheel lockage. Major subassemblies are hydraulic-electronic control unit that contains an actuating assembly with hydraulic-electrical pump, which supplies pressure for the brakes; Solenoids, which control the pressure of brake lines during ABS operation. The ABS computer uses information from four wheel speed sensors where electrical signals are produced by the wheel, and it determines hydraulic line pressure to prevent lockup and constantly checks for the system's failure. For this reason, when a warning light persists on the dashboard, recommending that the car should be checked by a professional before anything else, it suggests preliminary checking of the brake fluid condition, electrical connections, and fuses among others as the system is complex and should be checked by professionals for any repairs to be done. Every time when replacing wheel speed sensor, one needs to unscrew lug nuts, jack up the car, disconnect electrical connectors from the sensor, and then unbolting the sensor itself from its place, and in the reverse order with respect to the above sequence, one needs to bolt all the disconnected and removed parts to their places and tighten the lug nuts.
