Codos to Salcon for a well explained test procedure. Being an old-timer, I’d somewhat diagnosed the problem, but Saltos helped me to diagnose with certainty.
My stuck horn problem started with intermittent operation when locking my 2015 Chevy Silverado LTZ. It would sound some times, then would not at others, until it stoped sounding altogether.
One evening while waiting in line for gas at Costco, a pump became available, but the person in front of me was asleep at the wheel. In an attempt to awaken them, I pressed on my horn. This is the time it chose to not shut off (embarrassing).
Not knowing the location of the horn fuse, I preceded to drive home (approx. 2 miles), with the horn blaring. By the time I reached home, the horn had stopped. I could hear the sound slowly decreasing, until going dim permanently.
In my testing, I found there was a constant 12 volts at the horn connector, indicating I had a faulty horn relay (constant 12 volts at horn connector), and a bad horn (no sound although 12 volts present at horn connector).
The horn relay is built into the under-hood fuse box, which cost $180 from Chevy dealership. The horn was about $20 on Amazon.
Replacement of the fuse box was relatively easy. Instructions can be found on internet. The horn was as easy Access to the bolt required loosening the computer module and windshield washer reservoir. Even doing so required working in tight spaces, but perseverance got it done.
Horn working again, now on the the faulty passenger-side power mirror (not folding).
