Drive Range, Fourth Gear (Hydraulic Circuits): Notes
WARNING: This page is about a different car, the 2020 Buick Regal and 2019 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
As the vehicle speed increases, the transmission control module (TCM) receives input signals from the automatic transmission input and output speed sensors, the throttle position sensor and other vehicle sensors to determine the precise moment to command OFF the S38 solenoid. At the same time the S4 solenoid is commanded ON to regulate 4th clutch apply.