hmmmmm. You say the odometer is still working fine? Is the Odometer actually counting out your actual mileage or is it counting assuming you're going 45 all the time?
I was thinking it's something to do with the speedo sensor, but if you're positive the odometer is working perfect, then that eliminates the possibility of it being your speed sensor or the wiring. Sounds like something's messed up inside the cluster. I assume b/c you have a 99, you also have a tachometer?
Your best bet is to jus ask the dealer what they would charge to fix it, but the dealer is a master of emptying your wallet. I think the only thing you can do now is go to
http://car-part.com and search for "speedometer".
Make sure to find one with the correct mileage, you can actually find a used one for like $50, and it hooks up in about 10 minutes.
If you have a tachometer (RPM gauge) here are the following compatible (plug and play) years/models:
95-98 200sx SE
95-98 200sx SE-R (speedometer goes up to 150MPH but will still read accurately)
95-99 Sentra GLE
98 Sentra SE 2.0L (speedometer goes up to 150MPH but will still read accurately)
99 Sentra GXE-LE
99 Sentra SE(-L) (speedometer goes up to 150MPH but will still read accurately)
some models will have a security light built in, if you don't have an alarm, it jus won't light up.
Linear Mode
