They include Anti-lock Brake System (ABS) and Vehicle Stability Control (VSC) which ensure that a car remains steerable, stable in its direction and experiences the best rate of deceleration when there is hard braking on different surfaces. ABS, on the other hand, regulates the brake line pressure and wheel rotation rate , to avoid wheel lock up during hard braking and VSC helps to correct over/under steer. The Traction Control System (TCS) complements these systems, so that its job is to limit wheel spin onto acceleration from slippery roads. An element of the master cylinder the modulator regulates hydraulic pressure to the brake calipers with an electric boost pump to provide pressure and solenoid valves for regulating brake line pressure during system operation. The system has a specific sensor for each wheel, that produces a signal proportional to the wheel's speed and an electronic processing module. Front sensors are installed in the steering knuckles, and the rear ones are fitted in the rear axle housing. The ABS/VSC/TCS computer receives data from the sensors to adjust hydraulic line pressure so that it does not lock a wheel or allow it to spin freely and also constantly searches for problems. In instances where a dashboard warning light stays on, the system needs service and initial diagnostics involve the integrity of brake fluid, wires, and fuses. If problems continue, then professional diagnosis as well as repairs are required, because those systems are complicated. For removal of wheel speed sensor, some of the steps include loosening of the lug nuts on the wheels with regard to the side where the speed sensor is fixed, lifting of the vehicle and after that disconnecting the electrical connector of the speed sensor, succeeding removal of the nut that holds the sensor to the vehicle chassis and a slow withdrawal of the speed sensor, with regard to fixing, the process involves the reverse of the above mentioned steps.