The ABS module is attached to the HCU and forms an integral component. A 47-pin connector provides the electrical
interface between the ABS module and the vehicle wiring. The ABS module may be interrogated using the Land Rover
approved diagnostic equipment.
HYDRAULIC CONTROL UNIT
The HCU is a 4 channel unit that modulates the supply of hydraulic pressure to the brakes, under the control of the ABS
module.
The master cylinder primary and secondary circuit outlets are connected to the HCU primary and secondary circuits.
For additional information, refer to:
Hydraulic Brake Actuation
(206-06 Hydraulic Brake Actuation, Description and
Operation).
Each of the HCU circuits contains the following components to control the supply of hydraulic pressure to the brakes:
A normally open, solenoid-operated pilot valve, to enable active braking.
A normally closed, solenoid-operated priming valve, to connect the brake fluid reservoir to the dual circuit hydraulic
pump during active braking.
A hydraulic pump, to generate hydraulic pressure for active braking and return brake fluid to the reservoir.
Normally open, solenoid-operated inlet valves and normally closed, solenoid-operated outlet valves, to modulate
the hydraulic pressure in the individual brakes.
An accumulator and a relief valve, to allow the fast release of pressure from the brakes.
Filters, to protect the internal components from contamination.
The primary circuit also incorporates a pressure sensor to provide the ABS module with a hydraulic pressure signal.
Contact pins on the HCU mate with contacts on the ABS module to provide the electrical connections from the ABS module
to the dual circuit hydraulic pump motor, and the pressure sensor. The solenoids that operate the valves are installed
within the ABS module.
HCU Schematic Diagram