1-2/3-4 Accumulator Valves
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.
Line pressure is regulated into accumulator fluid pressure. Torque signal fluid pressure acting on the end of the valve basically controls this regulation.