Toyota 86510-AC010 Horn Assy, High Pitched

Disconnect the electrical connector from the horn and test it with battery voltage. If it doesn't sound, replace it; if it does, check for voltage at the terminal when the horn button is pressed. If there's voltage, check the ground connection. If not, inspect the horn relay and its wiring. If both have voltage, test the circuit from the relay to the horn button. If absent, check for an open circuit or replace the horn button. If continuity exists, check for an open or short in the circuit from the relay to the horn. For removal, disconnect the connector and remove the bracket bolt. To reinstall, switch the removal steps going from the last step to the first step.

If the relay is OK, check for voltage to the relay power and control circuits. If either of the circuits is not receiving voltage, inspect the wiring between the relay and the fuse panel.