1-2 Shift Valve
WARNING: This page is about a different car, the 2004 Pontiac Sunfire, 2004 Chevrolet Classic, and 2004 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The 1-2 signal fluid pressure holds the valve in the downshifted position against a spring force. Low/PRN fluid is routed through the 1-2 shift valve and into the Low band fluid circuit.