Hydraulic Control Unit

The HCU contains the Linear actuator, solenoid valves, the hydraulic pump motor and the pressure sensors used by the ABS for EBB, ABS and the various stability control systems. The ABS module and the HCU are attached directly together and not serviced separately. The brake fluid reservoir is the only serviceable component on the HCU assy. A new HCU comes with a new ABS module. When a new HCU assembly is installed, it must be programmed with the vehicle configuration information and programmed with the latest level of module software. These procedures are carried out using a diagnostic scan tool. Follow all scan tool instructions. For additional information, Refer to: Module Programming .

When an ABS, stability control system or EBB fault has been corrected or a new component has been installed, the ABS module must be calibrated. The calibration procedure is required for the stability control sensors to learn the zero-position of the vehicle. The calibration procedure requires the vehicle to be on a level surface and not moving. The calibration procedure (IVD Initialization) is carried out using a diagnostic scan tool. The vehicle must also be driven over 20 km/h (12 mph) for at least 1 minute on a fairly straight road which allows the ABS module to find the steering angle center.

This system does not incorporate a traditional master cylinder. All brake system function is controlled by the ABS module / HCU assy. The brake fluid reservoir is the only serviceable component on the HCU assy.