The Mark 20e Antilock Brake System (ABS) is designed to maintain the steerability of the car, the stability of its direction and the ability of the car to slow down on a particular road surface, to release or reduce the pressure on the brake line to avoid the lock-up of each wheel. It consists of three main components: the wheel speed sensors, the Hydraulic Control Unit or the HCU, and the Integrated Control Unit or the ICU; the latter receives input signals from four wheel speed sensors in order to detect near lock-up scenarios with tweaks hydraulic pressure by the use of solenoid valves. An 'ABS' warning light on the car's dashboard notifies the driver of system problems; these problems may be ascertained by inspecting the wiring harness for the ABS near each wheel for damages. Heating should be turned off before any of the electrical connections are loosened, and the ignition should not be on. If this warning light is on during operation, initial tests to check should include checking the brake fluid, make sure that electrical connectors are properly connected and properly inspect fuses and connects of wiring harnesses. However, if the above checks fail, one should seek help from professionals mainly because the system is complex. In order to have wheel speed sensor removal, the lug nuts must be loosened and the vehicle raised for the removal of the wheel. Check whether the ignition is off, find out the position of the sensor and remove the wires connected to the sensor and also remove the electrical connector, also take out the bolt holding the sensor and then, take out the sensor. Installation is done in the reverse sequence and always, there should be tightness on the mounting bolt and lug nuts before putting down the car.