S400-864-611-0 | Genuine Wabco® ABS ECU Electronic Control Unit 24V

Wheel Speed Monitoring

• Each wheel has a speed sensor that sends real-time data to the ABS ECU.

• The ECU constantly compares wheel speeds to detect if one is slowing down too fast (about to lock).

Decision Making

• If the ECU detects a potential wheel lock, it sends commands to the ABS hydraulic unit (also called the modulator).

Brake Pressure Control

• The ECU signals solenoid valves in the hydraulic unit to reduce, hold, or increase brake pressure to that wheel.

• This happens several times per second — creating the “pulsing” you feel in the brake pedal.

Result

• The wheels keep turning just enough to maintain steering control and stability while braking.

ABS warning light on the dashboard

Brakes locking up under hard braking

Pulsing or no pulsing when ABS should engage

Loss of traction or stability control

Communication errors when scanning with a diagnostic tool