OK so my jeep is back at it again with the funky issues. I have no inside back lights so I can't see my dash or my dials at night and my left taillight is out. The brake, reverse, and turn signals work just fine. Headlights and marker lights are fine. And my done lights work. The main problems here is the tailight. I use a GPS speedometer anyways cause of the bigger tires. So I've already pulled all my fuses and cleaned the necessary grounds and still nothing. I'm stumped. Could it be the socket itself?

Edit: its not the bulb because I swapped bulbs with the right side since I knew that it worked.

 

Bump

 

Take a continuity tester and you can see if the socket is getting power to it.

One thing to consider with the interior lights is if the headlight switch dims the interior lights (it did on my 2000 TJ) that is a failure point to check since everything would run through it. Beyond that, grab your wiring diagrams and electrical test tools and start checking the circuits.