Manual Valve
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The manual valve is moved to the NEUTRAL position and blocks line (2) pressure from entering the reverse (22) fluid circuit. The reverse (22) fluid circuit is opened to an exhaust at the manual valve.