Content Summary : Early Subaru Antilock Brake Systems The original Legacy Antilock Brake System (ABS) was licensed by Bosch and manufactured by Nippon ABS, Ltd. The system electronically controls brake fluidpressure supplied to the brake system. This control helps to prevent “wheel lockup” during braking on slippery surfaces and emergency situations. The system includesa fail-safe feature, which indicates a malfunction by illuminating the warning lamp.The system is then returned to a conventional power brake system. The four channel system provides accurate individual wheelspeed control and improves the directional stability of the vehicle during braking... The right half of the chamber is connected to the master cylinder (port 2) and to the pump in the HCU (port 6). The left half of the pressure chamber is connected tothe right rear hydraulic circuit (port 5). During conventional braking, the master cylinder pressurizes both sides of this chamber. However, if pressure in the left half of the chamber is lower than pressurein the right half, the plunger piston is allowed to move to the left. The other side of the mechanical valve contains a passage (zone E). One end of this passage is connected to the master cylinder (port 1); the other side is connectedto the pump (port 3). The passage is also connected through a pressure port to a second pressure chamber (zone D). This chamber is connected to the left rearhydraulic brake circuit (port 4). Also in this chamber is a second piston, piston 2.Piston 2 is connected to the plunger piston by means of a pushrod.