Pressure Control (PC) Solenoid Valve
WARNING: This page is about a different car, the 2009 GMC Yukon and 2009 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
Remember that the PC solenoid valve continually adjusts the torque signal fluid pressure in relation to the various PCM input signals (mainly the throttle position).