Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The TFP manual valve position switch consists of five fluid pressure switches: D2 and D3 are normally closed and D4, Lo and Rev are normally open. All fluid circuits routed to the assembly are empty and the TFP manual valve position switch signals the PCM that the transmission is in either Park or Neutral.