Tail Light Wiring Help Needed

You may have a bulb with the filaments shorted together, or even something wrong in a socket. I would start by:

Pull the kick panel connector loose, this will isolate the rear harness, and pull ou the rear lamp bulbs

"What you have" now is the tail light wire should go to both rear lamps, and the two turn/ brake conductors should be isolated. This means that if you put an ohmeter into the two socket terminals of each rear socket they should show open, as well as open to ground.

If the above checks out, leave the kick panel connector off, look up in your manual for the wire color/ pinouts to the that connector, and check that it has voltage at and when it should. IE tail lights on should power the tail circuit. The dome light circuit will be hot all the time. The turn / stop wires should only be hot when the brake pedal is pressed, or one at a time when the turn sig switch is operated with key "on"