My 2002 Chevy Tahoe blows the horn as I engage the starter. In other words, when I turn the key past ON to try and start it, the horn blows and that’s it. This all occurred while I was trying to replace the factory radio. I do have onstar if that makes a difference. I tried disconnecting the battery for thirty minutes. It worked once after ten minutes, but I tried to replace the factory stereo again and now it only blows the horn when I try. HELP!!! Please!

 

Sounds like passlock.