Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Component Functional Description - Hydraulic Control Unit (HCU) Assembly
The HCU Assembly internal components are slightly different depending on the brake system. The functionality of applying the brakes is also different. During an Anti-lock braking, traction control or stability control event, the functionality of the systems is relatively the same.
- NON-eBOOSTER SYSTEMS: The HCU on this system incorporates a Master Cylinder Pressure (MCP) Sensor, motor/actuator, hydraulic circuit pressure sensors, Inlet Valves and Outlet Valves. The Brake Pedal Position Sensor is external, and hard-wired to the PCM. The ABS Module in this system is capable of operating the motor/actuator inside the HCU to apply the brakes during an autonomous braking event. The vehicle operator can directly brake the vehicle by pressing on the Brake Pedal.
The Inlet Valves allow the fluid and hydraulic pressure to the calipers in each hydraulic circuit. The Outlet Valves are used to relieve the pressure in each circuit. There are two pressure sensors located in each hydraulic circuit that allow the ABS Module to monitor the pressure in the system for each circuit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.