I think it's probably something to do with the sending unit. That's the part that has the float and tells the gauge how much gas is in the tank. It's either a connection on the sending unit, or the unit itself.

 

I have the same problem with my 03 Ram 1500 5.7L. The code is high voltage level or something like that. I disconnected my battery while working on the CAI for about 20 minutes which provided a cold boot for the computer. I haven't had the problem for about two weeks.
Don't really no what the problem is/was but it had become pretty constant before the reboot.
If you identify the actual problem please post it.
Good luck...

 

Everybody that said to wiggle the connections on the tank is most likely right.
One of my friends had a 91 4runner and his started doing the same thing except it was dying and stop lights and wouldn't idle for more than 30 seconds without cutting off..

We replaced all the fuel lines, filter (BPITA!!), sending unit, injectors, and fuel pump..

It turned out to be a loose ground on the fuel pump causing all the problems. >_<

But hey, it had an all new fuel system when he sold it! lol