Hydraulic Control Unit

The hydraulic control unit is located in the engine compartment on a bracket attached to the frame rail. The brake pressure control valve block and pump motor are replaced as an assembly. It consists of the following components:

• Brake pressure control valve block.
• Pump motor.

Operation of the hydraulic control unit is as follows:

• During normal braking, fluid passes through four normally open inlet valves, one to each wheel.
• If the anti-lock brake control module senses a wheel is about to lock, it pulses the appropriate inlet 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, it opens the normally closed outlet valve which decreases the pressure trapped in the line.