Check your relay in the under hood fuse box. I ordered one from C-Dan, it arrived today. I swapped it out and my horn is working perfect now. $10 part vs buying new horns and them still not working.
HTH.
I am praying for a bad relay and dreading the possibility of horn contacts in the wheel. I have to sort it out before CM as it is on the pre-inspection check list.
Same dang thing just happened to me. It's not my fuse, although I haven't verified the relay yet. Interested to see what you find out. There are two horns on my LX, I'd be surprised if both went together but you never know.