My 05 Tahoe's headlights don't work on low beam. You can flip on the highs or switch over to the fog lights. I have checked fuses and relays all look good. I looked at the bulbs and the filament is good.
I am trying a new headlight switch but would I need to have it "programmed" or if I swap it out should it work immediately?

 

Welcome to the Chevrolet Forum. Might check the wiring at the switch to make sure it is the switch and not a wiring problem.