I have seen this problem before and I have it now.
This could be either a grounding problem back to the sensor in the gas tank, the internal gas tank levelometer or the cluster itself. However, mine is a 93 and we are therefore cousins of a kind. I moreover suspect the instrument cluster is hurt because of a water leak. I lost my speedometer and my first instinct was to replace the transmission sensor. I later disassembled the dash and found the interconnect film was corroded and connections were open. Daisy stepping with a soldering iron and I got that instrumentation back.
Personally, I will be replacing the cluster on my vehicule when I get the time. When I had the battery disconnected, the meter still would not zero. The movement is most likely hurt. It is a terrible inconvenience, I know. However, if you are familar enough with your vehicule's fuel economy, watching and resetting the mileage log after refueling is a work around (for now).
Fabe CBS, Newfoundland Canada