Theory Of Operation
WARNING: This page is about a different car, the 2012 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
The 2-3 Solenoid is activated when the Transmission Control Module (TCM) determines that the transmission must shift into or out of 3rd gear. The solenoid is only activated during the shifting of the transmission. When the solenoid is activated, hydraulic pressure is applied to the proper shift elements in the transmission to allow the desired shift. Once the shift is completed the solenoid is turned off.