Some models are equipped with an Anti-lock Brake System (ABS), the early and later 2WD models were with rear wheel anti-lock systems while the later models were equipped with 4-wheel systems on 4WD models. Through the wheel speed signals, Anti-lock Braking System monitors speeds and modulates the brake line pressure hence sustain steerability, stability, and optimum braking deceleration during extreme braking so as to avoid wheel locking. RABS is made up of computer module, anti-lock brake valve, exciter ring and sensor. To service the RABS module in 1993 and 1994 models; unplug the electrical connector of the module and get it off the instrument panel. For the 1995 and later models the center finish panel has to be pulled out, electrical connectors detached and the module then slid out. The RABS valve can be removed by disconnecting the brake lines and the electrical connector and unbolting it from the frame rail. Its installation involves placing the valve at the right place, connecting the electrical connector, and ensuring the brake line is tightly done. The speed sensor which is mounted on the rear axle housing require separation from the housing, cleaning and reconnection to the housing with a new O-ring seal in case of any defect. Exciter ring is designed to be serviced by disassembling the rear axle. The hydraulic control unit of Object 199's vehicle is mounted in the engine compartment and is responsible for the distribution of brake fluid and pressure in both simplistic and anti-lock mode. There are four wheel speed sensors for detecting the speed of the wheels and sending signals to the brake control module; this unit also contain self-checking abilities. Other indicators that are located on the dashboard are warning signs that inform the driver of faults, and the actions to take depend on the light. The main relay together with the pump motor relay is situated somewhere near the master cylinder. If a warning light is on, then attention is essential, and basic tests which require professional diagnosis and repair might be achieved.