Ok on my 2002 Sierra 1500 4x4.i have no fog lights. I have access to a advanced scan tool. I can command the fog lights the parking lights and the parking lot relay. Through the scan tool. I have gone through a diagnosis tree and it'* coming back to a bad connection at relay. Anyone have any ideas.

Stupid autocorrect. Also I can turn everything on through the scan tool. Could it be a bad bcm?

I would suggest you update in your original post. Did you take the switch apart and clean. If not here'* a video you can try to clean it to see if it solves your issue without spending money.