Original post by: joestenny ,
Its the taillight circuit board or a broken wire. If you look on here i asked same question and i posted up what the reason for my issue ended up being. Moat likely a bad or broken ground, circuit board that is on the back of the taillight or a broken wire. To figure it out get a test light clean a piece of metal connect teat light ground, then unplug taillight and stick trat light probe into 1 slot at a time see what works and what doesnt and write it down. Then go to the other taillight do samething.