A/T Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.) Assembly
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
Reverse fluid is routed through the 1-2 shift valve and to the TFP Val. Position Sw. Assembly, which signals the PCM that the transmission is in Reverse position.