Pressure Control (PC) Solenoid Valve
WARNING: This page is about a different car, the 2008 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
The change in throttle position (increase in percentage of travel) signals the PCM to increase the PC solenoid valve's OFF cycle time. When this occurs, higher filtered actuator feed pressure passes through the PC solenoid valve into the torque signal fluid passage.