Circuit/System Description
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Cadillac Escalade EXT. However, it is still accessible from the selected car via links, so may be relevant.
The shift solenoid (SS) 1 is part of the control solenoid (w/body and TCM) valve assembly. The assembly is attached to the lower control valve body and has no serviceable parts. The shift solenoid is a normally closed (NC), On/Off solenoid. When the TCM opens the solenoid ground circuit, (solenoid off) solenoid signal fluid exhausts and the clutch select valve 2 moves to the non-apply position. The TCM shifts the transmission by operating the solenoids in on/off combinations. Solenoid power is supplied by the TCM through a high side driver (HSD). The HSD protects the circuits and components that the TCM powers. Should the circuit overload the driver will shutdown. After the overload is removed the HSD reset.