This is a pretty common and annoying problem with the Dakotas'. Most likely it is the sending unit. You will have to drop the fuel tank and replace the fuel pump/filter assembly The sender, filter, and pump are all one assembly, so you'll need to buy a whole new pump assembly to change the sender. Of course you can, and should, also check your gauge to make sure that it is working okay. Use a meter to check your sending unit and see if you have any output. If that checks out, its your gauge. Here is a pretty good write up about how to do it....Hope this helps, good Luck.