Anti-Lock Brake System: Description

The Anti-Lock Brake System (ABS) consists of an ABS control unit, hydraulic modulator, system relays, speed sensors and necessary wiring. See Fig 1 .

When brake pedal is applied, the ECM monitors input signals from each wheel speed sensor. If ECM senses wheel lock-up, it will output a signal to appropriate solenoid valve. Each solenoid valve allows hydraulic pressure to increase or decrease to the appropriate wheel cylinder.

If a system failure occurs, the ANTILOCK warning light, located on instrument panel, will come on. System will be deactivated, but conventional brake system will still operate.

Fig 1: Locating ABS Components

Courtesy of AUDI OF AMERICA, INC.