same thing just happened about 3 weeks ago, went to napa. They don't even have the truck listed and couldn't help me. After I Left, problem corrected itself, yesterday...it starts again, go to check rear turn signal bulb, completely corroded, had to chip it out with a screwdriver piece by piece. Put new bulb in, same thing. I suspect socket is no good, even after cleaning it out with contact cleaner and trying to clean the socket with emery cloth, still no good.