Chosen Solution
My 2007 Coroll LE horn often honks when the steering wheel is turned. Sometimes the horn honks when car is parked with engine off. Removed fuse as temp control option. Dealer wants $130/hr just to diagnose problem.
i guess it only can be a damaged Cable, like it has a crack in it and the cracked part connects to some Metal Part on the car and so a short circuit happens. So at first you should have a look at the Cables going to the Horn, and on the Connectors. (Sorry for the Bad English)
