Well, it is normally the potentiometer that it is in the gas tank, you can check it from the sig. Way remove the gasoline pump even side, it is a float without giving the veículo, it opens the swich and lets the float fall with natural will you see that it will not mark anything, after verifying that the float goes up and keep it for a few seconds, if on the board it does not rise the level of petrol Get out of the Eye Potentiometro, this carries the 12 -volt signal and the signal that comes to the board is varied according to the position of the float if nothing comes out to this the problem does not work the potentiometer eye in some veículos is a sign of earth