Once you have located the engine compartment fuse box, open the cover and look for the horn relay. The horn relay is a small, black relay with a green connector. It is located in the upper right-hand corner of the fuse box.
If the horn relay is faulty, it can prevent the horn from working. To test the horn relay, remove it from the fuse box and connect a 12-volt power source to the terminals on the relay. If the relay is working properly, the horn should sound.
If the horn does not sound, replace the horn relay. The horn relay is a relatively inexpensive part that is easy to replace.