Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly
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.
Lo fluid is routed to the TFP manual valve position switch where it closes the normally open lo pressure switch. The addition of the lo pressure switch being closed signals to the PCM that manual first is selected.