A couple of weeks ago I was unloading my truck when the horn gave a short beep, a few minutes later it did it again this time longer, it continued getting more frequent and longer until eventually it was continuous, at that point I had to pull the fuse. I have code P2509 (intermittent power to PCM/ECM) showing due to recent battery problems, now replaced. The horn still goes off if I replace the fuse. Any ideas as what to check would be greatly appreciated.

-George-