I'd suggest downloading the wiring diagrams to your DOCUMENTS. Then go to the page that deals with the HORN. Then look at the source of power on that diagram. IN this case it's on the BATTERY BUSS (B) and then look for the numbers 9 followed by the number 4. After determining that go to the POWER SYSTEM page, at the beginning of the wiring diagrams and follow the B line to the number 9 and then from the number 9 to the number 4. At that point you find a 20a fuse on the battery bus.
So then go look at the upper right hand corner of that POWER SYSTEM page, and you can see where the 20a fuse on the battery bus is located.
Looking at that fuse box in the upper right corner of the POWER SYSTEM page, you see rows of fuses with the letter (B) under a row of fuses indicating that row of fuses in on the battery buss. On other rows you see (IG1) and (IG2). Those rows of fuses only have power when the key is put to ON. The (ACC) row of fuses is just what you think, fuses on the accessory buss and powered when the key is to ON or ACC positons.
IG1, IG2 and ACC never have power with the key to off or out of the switch. IG2 has power with key to ON but no power if the key is put and held to START.