Isolation Valve
WARNING: This page is about a different car, the 2000 Land Rover Range Rover and 1999 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.
The isolation valve is made up of an inlet and an outlet solenoid valve. During ABS braking, the isolation valve disconnects master cylinder from the servo cylinders and connects servo cylinders to brake fluid reservoir return.