Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The Pressure Control Solenoid 1 (PCS1) is a solenoid that controls pressure which is proportional to the current. The transmission fluid pressure from PCS1 is directed to another valve which regulates the transmission fluid flow and pressure through shift valves that allows it to engage different clutches.
The transmission control module (TCM) provides B+ to PCS1, the torque converter clutch (TCC) solenoid, and the main modulation/line pressure control solenoid (MAIN MOD) through a separate solid state device called high side driver 1 (HSD1). The TCM uses a low side driver to control the current flow to the PCS1. The TCM controls the current to the solenoid by changing the amount of time that the low side driver is on.