Why wont my tail lights work

Do you know how to read a wiring diagram and diagnose a wiring issue. If you do then pick up a chiltons and work through the wiring. If you don't then I can't provide you much info outside of that. I don't know off hand how these are wired. I'm thinking there is a possibility it may be a headlight switch. I don't have a diagram to see whether it could be or not.

if its the running/parking lights that arnt working check for power at lights when u have them on, if no power go to the fuse block and find the fuse for running lights or parking lights maybe blown fuse or something

bad ground connection i had that problem

If your dash lights are out to and the fuse is good look for power at the fuse box if yes your wires under the bed are either cut or apart check tje brn wire for continuity

I had a similar problem with my 1994 GMC. In addition to the tail lights not working my instrument panel didn't light up. I replaced the instrument dimmer switch and that also fixed the tail light issue.