I own a 2002 rodeo and my left rear break light does not work when my parking and or headlights are on. It works fine otherwise.
Anyone have any idea what might cause this?

do you have a trailor light towing harness? there seems to be a lot of odd electrical issues if the harness isn't hooked up properly. try removing that (if you have one) then see if the problem persists.

let me know if this works for you