So ive read a thread similar to this but not the exact same. Also the solutions that were suggested didnt work for me. so here it is.

I have a 98 sport. When i turn my right blinker on my rear right blinker and tail light flash, as well as my left tail light (not blinker). The same thing happens when i turn on my left blinker except the opposite. The front blinker lights function properly. I replaced the combination/multifunction switch but the problem didnt go away. Im lost and have no idea what the problem could be. Any suggestions would be greatly appreciated.

 

Checks for shorts at the sockets for the bulbs. Have you find a wiring diagram to follow yet?

 

You most likely have bad grounds for the bulbs. When that happens, the electricity will find anyplace it can to go, which makes other stuff light up

 

Yeah well you need to get in to the rear end of that xj and you will find green goopy connectors behind the tail lenses. Take them out, You can jumper the wires across the bad connectors, one by one.