Outback [Legacy] AWD F4-2.5L DOHC (1996)
Hydraulic Control Assembly - Antilock Brakes: Description and Operation
ABS
HYDRAULIC CONTROL UNIT
The hydraulic control unit is a fluid pressure control assembly which consists of an electric motor, plunger pump, plunger piston, housing, solenoid
valve and a relay. The solenoid valve moves to three positions, as shown in figure. When it is moved to position "1" (current "OFF"), the master
cylinder and brake system are connected to each other. With the valve moved to position "2" (part of current flow "ON"), all passages are closed.
At position "3" (full-current flow "ON"), master cylinder ports are closed and the line between the hydraulic unit reservoir is connected to the
brake system
As wheel deceleration exceeds the specified deceleration setting during braking, the solenoid valve moves to position "2" to hold brake fluid
pressure. Further deceleration increases moves the solenoid valve to position "3" 50 that brake fluid pressure is released and, at the same time, the
motor starts to drive the plunger pump. When wheel deceleration stops, the solenoid valve is held at position "2" to maintain brake fluid pressure.
