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 TCM provides B+ to shift solenoid 1 (SS1), shift solenoid 2 (SS2), shift solenoid 3 (SS3), and pressure control solenoid 2 (PCS2) through a separate solid state device called high side driver 2 (HSD2). The TCM uses low side drivers to control the solenoids.