My back turn signal light is not working!What could be the reason?And why its indicator on my dashboard is blinking like crazy very fast unlike right one.I would like to know how much will cost to fix it so won't get fooled.Thanks in advance!

the bulb is burnt out it blinks fast on the dash to tell you this. You can by the bulbs for like $5 at autozone, advance auto parts and fix it yourself or drop about $30 at the dealership.