1-2, 2-3, Reverse Shift Solenoid (SS) Valve Assembly (S3)
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 1-2, 2-3, reverse SS valve assembly is de-energized, allowing fluid pressure to build-up in the S3 signal (16) fluid circuit.