An anti-lock braking system, or ABS is a safety system which prevents the wheels on a motor vehicle from locking while braking. Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The basic hydraulic braking system consists of ABS hydraulic control valves and electronic control unit, brake master cylinder, necessary brake tubes and hoses. The ECU constantly monitors the rotational speed of each wheel, and when it detects a wheel rotating significantly slower than the others it actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, reducing the braking force on that wheel.
The following anti-lock brake system apply for 1997 Honda Accord. The circuit consists of ABS Control Unit, ABS pump motor relay, ABS fuse/relay, modulator unit, brake fluid level, instrument cluster, alternator, parking brake switch, right/left rear wheel sensor, right/left front wheel sensor, ABS inspection connector, pump motor.