So what have you tried so far? Is this the first time it has acted up? Have you added fuel or driven a considerable distance to see if the gauge starts working again at different fuel levels? If so, I have an inexpensive fix, but without some information, anything would be a guess.
The closest I have is a 1997 service manual. The fuel gauge sending unit signal goes into the Body Computer which feeds the instrument cluster. Any break in the sending unit circuit will cause the fuel gauge to read full. The most likely culprit is the sending unit itself which can be easily repaired.
The first thing to do to narrow down / verify the cause is to unplug the four-pin fuel pump connector, then connect the dark blue wire to the black wire, (not the black wire with a tan stripe), with a paper clip between the two connector pins, turn on the ignition switch, and watch the fuel gauge. It should go to "empty". If it does, the only cause can be a bad connection on the sending unit. This is repairable.
If the gauge still stays on "full", ground the dark blue wire to a shiny metal part of the car body. If the gauge goes to "empty" now, the black ground wire is open. The pump motor has a separate ground wire so any little voltage drop in it won't affect the gauge reading. That means the fact the pump runs can not be used as a clue to this problem.
If bypassing the sending unit makes the gauge read "empty", drive the vehicle a few hundred miles after filling the tank. Typically the gauge will start to work properly when the fuel level is somewhere between 1/4 and 3/4 tank if the sending unit is the problem. That's why I asked if you added or used fuel since the problem started. It's an important clue.
Wednesday, August 5th, 2009 AT 5:00 PM