Hybrid Low, 1-2 Clutch Regulator Valve
WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
PCS 3 signal fluid moves the hybrid low, 1-2 clutch regulator valve, against hybrid low, 1-2 clutch regulator valve spring force, to the applied position. This allows line or auxiliary line fluid to pass through the valve into the HL 12 clutch/4th clutch feed circuit.