This is a relatively common problem on these Jeeps. You have a short in your taillamp housing. Remove your taillamp housing and twist the affected bulb socket until your light begins working. This is a temporary fix, but your problem will return.
The only complete repair is to replace the taillamp housing assembly with a new one. The new one will come with new bulbs and sockets so you just have to plug it in.
I hope this helps! Let me know if you have any more questions!
I said to twist the bulb socket, not the bulb. You will find that they will start working, but only temporary. You can try and bend the metal tabs, but it is only a temporry fix.
THe correct fix is to replace the taillamp assembly.
That is it, and that is a relatively good deal, the dealer wants over $100 for it.
Replace that nad you will be good to go.
P.S. Parts train will spam your mailbox all the time, so if you have a spam email you use, use it.