1-2, 3-4 Shift Solenoid (SS) Valve (315A)
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
De-energized (OFF) by the PCM, it exhausts 1-2, 3-4 signal fluid through the solenoid thereby creating a low 1-2, 3-4 signal fluid pressure in the circuit. Low 1-2, 3-4 signal fluid pressure allows the 1-2 shift valve to move to the upshifted position.