The 2-3 Shift Solenoid (SS) Valve
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The 2-3 SS valve is de-energized (turned OFF) by the PCM, which allows fluid in the solenoid valve circuit to exhaust. Filtered actuator feed enters the solenoid valve circuit through orifice #16. This feed exhausts though the solenoid valve.