1-2 Shift 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.
High fluid pressure from the 1-2 shift solenoid (SS) valve holds the 1-2 shift valve in the downshifted position. The valve allows fourth band fluid from the fourth servo and from the 3-4 accumulator piston to pass through the valve. Fourth band fluid then enters an exhaust passage where the fluid is routed through orifice #2 before exiting the circuit.