Toyota 86520-08020 Horn Assy, Low Pitched

Before beginning electrical diagnosis, check the fuses. Disconnect the electrical connector from the horn. To test the horn, connect battery voltage to the terminal with a jumper wire; if the horn doesn't sound, replace it. If the horn does sound, check for voltage at the terminal when the horn button is depressed, ensuring to check for power at the horn terminal near the mounting bolt. If there's voltage at the terminal, check for a bad ground at the horn. If there's no voltage at the horn, check the relay, noting that most horn relays are either the four-terminal or externally grounded, three-terminal type. If the relay is functioning, check for voltage to the relay power and control circuits; if either circuit is not receiving voltage, inspect the wiring between the relay and the fuse panel. If both relay circuits are receiving voltage, depress the horn button and check the circuit from the relay to the horn button for continuity to ground. If there's no continuity, check the circuit for an open; if there's no open circuit, replace the horn button. If there's continuity to ground through the horn button, check for an open or short in the circuit from the relay to the horn. For 2007 and later models, remove the front bumper cover, disconnect the wiring, and remove the bracket bolt. Installation is the reverse of removal.