Anti-Lock Brake System: Operation

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

With engine running and vehicle speed more than 4 MPH, pump motor will operate for a short period of time and may be heard inside vehicle. During pump motor operation, ABS system completes a self-check. During ABS system operation, brake pedal pulsation and steering wheel and vehicle body vibration may be experienced. These conditions are normal.