Anti-Lock Brake System: Operation
There are 3 normal modes of system operation. In No Braking mode (when vehicle is first started), the ignition switch is in RUN position. ECU performs a self-check, an external circuit check and begins operation. When brake pedal is fully released and vehicle speed reaches 3 MPH, ECU performs an electrical and hydraulic check of pump and solenoid functions.
In Normal Braking mode (driver applies brakes), the ECU does not affect either front or rear brake hydraulic functions. The ECU monitors each of the 4 wheel speed signals in preparation for possible initiation of anti-lock control.
In Anti-Lock Braking mode (wheel speed signals indicate a wheel is about to lock-up), ECU operates 4 independent control solenoids to increase or decrease pressure as necessary to prevent wheel lock-up. This function continues as long as necessary during braking.
The ABS system also has a Failure mode. When system detects a malfunction, the ECU disables anti-lock braking and allows normal braking only. System then stores Trouble Code(s) and illuminates ABS Warning Light. Trouble codes are later retrieved for diagnosis through use of the Hyundai Multi-Use Tester (MUT).