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I have a 1999 Corvette and the horn went off on its own several times. Finally blew fuse and with the fuse blown it is still draining the new battery dead. Why?
If the horn is going off by itself the "control side" of the relay is finding a ground and not by you pressing the horn switch is what normally happens...see the picture (2001 horn circuit) and your short to ground may be anywhere in yellow highlighted area...I'd say remove horn relay 36 and look on the bottom of the relay you are looking for pin 85....86 will be hot...if you have an ohm meter probe pin 85 and touch the other end of the ohm meter to a clean ground...anything OTHER than an open circuit means you have a short...it can be anywhere along there !!...there is a connector C209 in there too...the horn relay control grounds the control side of the horn when you press the panic button...the BCM makes that happen !!...and as you can see pin 86 and 87 share the same power wire...87 when energized closed then goes to the fuse !!...when you do "short to ground" testing both ends of the circuit must be disconnected.
