2008 Envoy. Key off. Even with the dome light override button pushed, the dome lights come on when the rear wiper switch is turned off. Turn the wiper switch on and the dome lights go out. I haven't found a wiring diagram for the dome lights yet but it seems like something is triggering the BCM to turn the lights on. Pulling the TBC3 fuse makes it stop. Any ideas? Wiring diagrams for dome lights and rear wipers?

 

The first thing I would try is cleaning the grounds. Bad grounds can cause all sorts of weird electrical issues.