Park - Engine Running (W/O Electronic Range Select Mode): Notes
WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
When the gear selector lever is in the Park (P) position and the engine is running, fluid is drawn into the oil pump. Line pressure is directed to the pressure regulator valve.