i dont know much about cars at all and i have this problem. my speedometer is working incorrectly in the sense that about 50% of the time i am driving, it reads )mph and the other 50% it is bobbing around or below the speed i am going at. my odometer only counts my miles when my speedometer is reading above 0 mph, and when it is counting, it is obviously not counting the actual milage bc the speedometer is never correct. on a related note, my gas guage has as far as i can remember been reading about 1/3 lower that what i actually have in the tank left. becuase of that i have used the odometer to know when i need gas because i know how many miles i get per tank. ive been dealing with this problemfor a couple of months now and i really need to take care of it. can anyone help me understand what the cause of this problem is and what i need to do to get it fixed.

ps. ive taken it to a shop and they tested the alternator and battery and stuff and said it was probably an electrical problem and the reffered me to a specialist, but it would help if i had an idea of what could be wrong before i go in there.

 

When my accord did this it turned out to be the speed sensor.
If you do a search there are a load of post about where this is and even pics.
Local bone yard $5-$15 bucks

Everywhere else R.I.P.

New the average from $45 - $280 this all depends on where you shop for parts.
good luck