I have a 1997 Honda Civic and am having this problem now also. It happened awhile ago but I never bothered to chase after fixing it. I figured it must be the sending unit or whatever is connected to the gas tank float arm. Usually it is a variable resistor that changes the current (thus voltage) sent to the fuel gauge. If that thing is off burnt or shorting out, then the meter reads full.
I have noticed that sometimes when I start out on a trip (Car is cold) the meter does not pin full but seems to function normally. But as I drive the meter will eventually go up and peg at full gas tank indication. So it seems to be heat related (like something is getting hot and changing value). Or maybe it could be a mechanical problem like the float arm pivot getting rusty and not swinging freely with the gas liquid level. It could be getting sticky and held up in the gas full position. Just my educated guessing here as I've not looked into this yet at all.
I'll need to find my old Civic Service Manual buried somewhere in the house to troubleshoot it one day.
Sunday, January 20th, 2008 AT 9:17 PM