Anti-Lock Brake System: Operation

Each Wheel Speed Sensor (WSS) sends an AC electrical signal to ABS Electronic Control Unit (ABS-ECU). The ABS-ECU translates this information as wheel speed. When any decelerating wheel speed rate is determined to be excessive in comparison to other wheel speeds, the Hydraulic Control Unit (HCU) cycles hydraulic brake pressure to each wheel to equalize speed of all wheels. ABS turns itself off when vehicle slows to 4 MPH. Minor lock-up may occur at this point.