3-4, 4-5 Shift Solenoid (SS) Valve Assembly (S4)
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
Line (2) fluid passes through orifice #4 into the S4 signal (17) fluid circuit in preparation for a shift. The normally open 3-4, 4-5 SS valve assembly is OFF, allowing any fluid pressure in the S4 signal (17) fluid circuit to exhaust through the solenoid.