Primary Pressure Regulator Valve
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
Reverse (22) fluid pressure, at the primary regulator valve plunger, boosts line (2) pressure for the additional torque requirements in REVERSE. Throttle signal (10) fluid pressure from the line pressure control solenoid valve (SLT) acting on the primary regulator valve plunger also helps determine line (2) pressure in REVERSE depending on throttle position and other TCM input signals.