I have a 1999 (new body style) Sierra 1500 4x4. The horn on the sterring wheel doesn't work. I have removed the air bag and tested the contacts. No power coming up to them. I them traced the wiring down the a module under the steering column to a purple connector on it. The number one wire was corroded so I sprayed a cleaner into the connector and then a metal protector. The forn worked for about two weeks and stopped again so I checked this connector again and all looks fine. If I hit the panic button on my remote the horn sounds and also when I hit the lock button on the remote several times. I can't find a wiring diagram for the horn. Could this module under the steering column be defective? Or should I look somewhere else? Thanks.

 

I found the problem. Seems to be a bad connection with the horn contact wires under the air bags. I removed the spring loaded connector and cleaned it up. Works fine now.