Toyota 86520-01050 Low Note Horn

Before beginning electrical diagnosis, check the fuses. First, disconnect the electrical connector from the horn. To test the horn, connect the battery voltage to the horn terminal with a jumper wire; if the horn doesn't sound, it needs to be replaced. If the horn does sound, check for voltage at the terminal when the horn button is depressed. If there's voltage at the terminal, inspect for a bad ground at the horn. If there's no voltage at the horn, check the relay. If the relay is functioning, verify voltage to the relay power and control circuits; if either circuit lacks voltage, inspect the wiring between the relay and the fuse panel. If both relay circuits receive voltage, depress the horn button and check for continuity from the relay to the horn button to ground. If there's no continuity, look for an open circuit; if no open circuit is found, replace the horn button. If continuity to ground exists through the horn button, check for an open or short in the circuit from the relay to the horn. To access the horn, open the hood; it is located in front of the radiator. To replace the horn, disconnect the electrical connector and remove the bracket bolt, then install the new horn by reversing the removal process.