Hydraulic Control Unit
| ITEM | DESCRIPTION |
|---|---|
| 1 | Brake pipe to LH front caliper |
| 2 | ABS module |
| 3 | Brake pipe to RH front caliper |
| 4 | Master cylinder primary circuit connection |
| 5 | Brake pipe to LH rear caliper |
| 6 | HCU |
| 7 | Brake pipe to RH rear caliper |
| 8 | Master cylinder secondary circuit connection |
The HCU is located on the rear LH side of the engine compartment and is an integral component with the ABS module. 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 primary and secondary outlet ports of the master cylinder are connected via 8 mm (0.315 in) diameter brake pipes to the primary and secondary circuits of the HCU. The primary circuit in the HCU provides 2 separate outlet ports to the RH front and LH rear brakes. The secondary circuit in the HCU provides 2 separate outlet ports to the LH front and RH rear brakes.
The HCU incorporates 3 brake operating modes as follows:
- Normal braking/Electronic Brake Force Distribution (EBD)
- ABS braking
- Active braking.
As the HCU and ABS module is a fully integrated unit, the description and operation details for the HCU and ABS functionality, including the 3 braking modes, are detailed in the Anti-Lock Control - Stability Assist section of the service information.
For additional information, refer to: ANTI-LOCK CONTROL - STABILITY ASSIST .
SERVICING INFORMATION
The ABS module and HCU form a single component and must not be separated. The ABS module and HCU assembly is supplied in a pre-filled state. After installation, the hydraulic brake system only requires a conventional bleed of the system; there is no requirement to pressure bleed the system.