There is only one switch/valve and it is located in a fitting on the drivers side of the pump appearing to be screwed into the plastic part of the pump. (It actually screws into a fitting on the pump behind the plastic).
Open would mean infinite resistance, or an broken or open wire somewhere. It might be possible the switch has failed. If so, you should find that you have high levels of assist all the time. Steering might seem floaty. The switch is used to regulate fluid flow based on various inputs including road speed, brake application, and rate of turn.
Start with looking at the wires. Check the connector. yep, it's a pain as the stuff is buried.