Quick Noob question
 

My rear passenger running light is out. Not my brake light. Just the red light that is on when your headlights are on. I tried a new bulb, and it is only the passenger side. I dont think there is a fuse for ONLY that light. Any suggestions?

Light tester. You can pick one up for cheap.

Then after that multimeter. You can check continuity to see if you are grounding out or if you even have ground there.

Most Jeep electrical problems come from poor grounding. It has been advised many times on this forum that if you have to fix something to slap another ground to the electrical component in the process.

x2 remove the boot linning [trunk] on the appropriate side and have a mess with the wiring, and as said add an extra earth if possible