Transmission code p1810

I just got a 2000 malibu LS and when I scanned it I got the p1810 code. I looked it up and it says it is the TFP Valve Position Switch Circuit. The transmissin shifts hard but makes no noise. Does anyone know how to fix this and where I can get one, like the part number or something. I would appreciate any advice.

Thanks,
James

Does the transmision bang hard when you put it in gear? On my 01 Mailibu it was the intake air temperature harness and plug that went bad. Transmission would bang very hard in to gear and then shift gears very hard.