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 keeps the 1-2 shift valve in the downshifted position. Low/PRN fluid continues to feed the low band fluid circuit.