Scion 86510-28130 Horn Assy, High Pitched

Regarding electrical diagnosis, start with the fuses. Initially, remove electrical connection terminal of the horn. To check the horn, apply battery voltage across the horn terminal with a jumper wire; if the horn does not sound then it should be replaced. If the horn does sound, then with the horn button pressed, and supply voltage at the terminal next to it. If the is voltage at the terminal, look for the defective ground at the horn. If you do not get voltage at the horn, examine the relay. If the relay is good, jumper across the relay power and control circuits to apply power; if no voltage is present in either circuit, examine the circuits' wiring between the relay and the fuse panel. If you are getting voltage to both of the relay circuits, push in the horn button and scope the circuit between the relay terminal and the horn button for continuity to ground. If there is no continuity, check for the open; and if there is no open then replace the horn button. If horn is tapping through button, check for opens or shorts on the circuit for the relay to the horn. For 2001 through 2003 models, there are two horns: one behind the right headlight and the other located in middle of front of engine hood; the center horn however is housed at the center of front bumper and thus will entail the owner to first undock the front bumper cover. To replace horn, remove the horn's electrical connector and then remove the bracket to bolt, and the installation is done in reverse method pursued in their removal. For the models produced after 2004 you need to take off the front bumper cover to reach either horn, whereas to access the horns on the vehicle manufactured after 2010 you can separate the upper screws and slightly pull the bumper cover forward. To replace a horn it is necessary to unplug the electrical connector and unbolt the bracket from the horn, while the procedure for installation is opposite from that of removal.