my passanger tail light doesnt work but the brake light works the drivers side is perfect. the bulb is fine to changed it and put it on other side it worked. what could be wrong. signal also works. thanks

I'm assuming you checked for 12 volts on the right rear brown (tail light) wire. Using a meter or tester light you should have power to a good ground when you turn on the lights.
Check that first. If so:
Try providing a ground directly to the light. Take a test jumper wire and touch the light bulb base right where it meets the glass.
Touch the other end of the test jumper wire to a known good ground.
Turn on the lights and see if that makes the light come on. If so, chances are the socket is bad or the ground wire isn't getting a good ground.

Is the lic. plate light working ? The running lights in the rear all work off the same power feed from left bulb to lic. plate to right bulb. I think you have a problem with the rear wire harness open it up and look for a wire damage
MIKE