The anti-lock brake system works to retain vehicle manoeuvrability, directional control and best straight line stopping distance in all types of roadway surface and severe brake conditions by selectively applying pressure to the brake cylinder of every wheel in relation to its rotational speed to avoid wheel locking. It consists of three main components: A number of components including the wheel speed sensors, the Electronic Control Unit (ECU) and the Brake Pressure Modulation Valve (BPMV). There are four wheel-speed sensors which send variable voltage signals to the control unit to decide whether a wheel is about to lock up and signals the hydraulic unit of the necessary pressure level. A symbol named "ABS" appears in the car dashboard that flashes to tell its owner that there's a problem, those problems can be diagnosed by physically checking the wiring harness of the ABS that connects to the car's control module and looking for signs of damage near each wheel. Care should be taken so that the ignition is turned OFF before tackling electrical leads. Traction control is also part of some cars, which uses the ABS system and relays it to the engine fuel maps based for wheel rotation and prevents wheel spinning. If a dashboard warning light stays on, ABS requires service; initial diagnostics are viewing brake fluid level, connecting terminals and wires, checking fuses, and inspecting wiring harnesses. In case of complications, the item ought to be diagnosed and corrected by a professional technician. To remove the wheel speed sensor information or replace it, some steps to follow are as follows; the ignition to off, the lug nuts loose, the car should be raised, and the wheel should be detached. Disconnect the wiring of the sensor, on remove the bolt holding the sensor and slowly pull it off. Installation on the other hand is done in the reverse order accompanied by the tightening of all the screws.