2-3 Shift Solenoid (SS) Valve
WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.
This solenoid remains de-energized as in fourth gear and the signal B fluid exhausts through the solenoid.