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.
Mechanically controlled by the gear selector lever, the manual valve is in the PARK (P) position and prevents line (2) pressure from the primary regulator valve from entering the drive (19) and reverse (22) fluid circuits.