2004 Dodge Intrepid transmission

It can be a number of things it depends on what its doing. What you are experiencing is what they call "limp mode". It shifts to 2nd gear and stays there untill you restart your engine. My 2003 stays in overdrive and will not shift at all until I come to a stop, them it goes into linp mode but it doesent do it all the time. I suggest you take it to a dealer and let them put it on a diognostic machine. It may only be a sensor.