2004 lly with a 26gallon tank. when the gauge says empty i fill it up but the most it will take is 12 gallons so theirs 14 gallons still in the tank why would the gauge say empty and still have fuel. bad sensor?
when you run the gauge down does the refuel dummy light come on? if the light does not come on then then it could just be your stepper motor. However it is probably the sending unit. they seem to enjoy going out/getting mis-calibrated. You should be able to go through your efi and reset the values in case they somehow got messed up as well if you have a v2. But I'm sure rob probably did that when he created your tune. but it never hurts to check the resistance before dropping the tank for the sender. Should be at 0 empty and 80ohms full.