If the horn relay is in the underhood relay box-- I believe it is-- it'll
be labeled on the fuse/relay box lid. Pulling the relay will prevent
battery drain from a shorted horn switch.
When you're ready to check the horn switch, disconnect the battery ten
minutes prior to working on the car. This should allow the air bag
computer to discharge its capacitors. Then, with the battery
disconnected, check the system. Any wiring with yellow tape on it will be
for the air bag system. Don't do any testing on this wiring. If you need
to reconnect the battery to continue testing the horn, it's okay to do so,
but *do not*
(dis)connect any air bag components or do anything with the
air bag wires while the battery is connected. Also, do not turn your key
on. If the air bag is removed and you turn the key on, your air bag
system will recognize that there is an open circuit in the driver's air
bag circuit (because the air bag is not there) and turn on the air bag
lamp. Then you'll need to take it to the dealer to have it turned off.
If you've reconnected the battery, disconnect it and wait another ten
minutes prior to doing anything additional with the air bag system.