just get a new gauge if the gauge is faulty! used ones are peanuts! i got a cluster with everything for about $30. As for the OBC (if thats what you re refering to as a computer unplug it and check the connector is ok and make sure its plugged in correctly and tight ! I am pretty sure though that both the fuel and temp gauge faults will only be solved for good if you replace them. Had the same problem too!
"Lo there do I see my father.
Lo there do I see my mother.
Lo there do I see my brothers and my sisters.
Lo there do I see the line of my people back to the beginning.
Lo they do call to me
they bid me take my place among them in the Halls of Valhalla,
where the brave may live forever"