Fog lights on '01 Suburban won't work

Hey guys, I've bought a 2001 Suburban about a month ago. Everything's great except I can't get the fog lights to work. I believe I've checked all the fuses and relays, changed the bulbs and it still won't work. The little light below the fog light switch doesn't come on when you push the switch. Any ideas? The only thing I can think of is either a bad switch - which doesn't seem likely, does it? - or maybe whatever tells the fog lights that the hi-beams are on or off isn't working properly. All the connections are good as far as I can trace. Anybody have any thoughts on this?
Thanks a ton!

Fog lamp relay is controled by the BCM.
The switch sends a ground signal to the BCM and then the BCM commands the fog lamp relay

I don't understand. What is the BCM?
Thanks

Body Control Module

I tried a friend's switch that I know works and it didn't help anything, so it's not the switch. I took it in for diagnostics and they said the BCM isn't recieving a signal from the headlight switch that they're on, so the fog lights don't know the headlights are on and they won't work unless the headlights are on. Got any ideas about what might be the problem or maybe how to bypass the BCM? I believe I've checked all the connectors in the line and everything seems good. Bad wire? I don't know.