Hydraulic Control Assembly - Antilock Brakes: Description and Operation

HYDRAULIC ANTI-LOCK ACTUATOR
Components
The hydraulic anti-lock actuator consists of a valve body assembly, pump and a motor assembly. During normal braking, fluid from the brake master cylinder enters the hydraulic anti-lock actuator through two inlet ports located on the bottom of the hydraulic anti-lock actuator. The fluid then passes through four normally open Isolation (ISO) valves, one to each of the four wheels.

System Operation
If the anti-lock brake control module senses that a wheel is about to lock, the anti-lock brake control module pulses the appropriate ISO valve, which closes that valve. This prevents any more fluid from entering the affected brake. The anti-lock brake control module then looks at that wheel again. If it is still decelerating, the anti-lock brake control module pulses the normally closed dump valve, which decreases the pressure trapped in the line. The hydraulic anti-lock actuator, the valve body, the pump and the motor are not serviceable separately.