IQ Horn Activated When Ignition Off

[mds33]

IQ 2014 auto was parked, locked, after approx 15 minutes the car horn, not the alarm, activated continuously. When engine started, horn went off stopped when engine started.

Fuse and relay OK no breaks in wiring.

Any thoughts why it sounds when engine/ignition off?

This is not a ‘one off’. 

[Bper]

Hi Mike,its possible that a malfunction is in the horn switch itself or the circuit. If the switch becomes stuck in the "on" position, it would continuously activate the horn, even when the engine is off and the ignition is off. This could explain why the horn stopped when the engine was started, as the power to the horn circuit may have been interrupted when the engine was running.

Replacing the horn switch may likely resolve the issue. I would also check the horn circuit for a possible short of damaged cable.Use a multimeter for continuity.Disconnect the electrical connector from the horn switch. Use the multimeter to check for continuity or resistance across the switch terminals while pressing the horn button. If there is no change in continuity or resistance when the button is pressed, the switch may be faulty and need replacement.Hope this helps

[flash22]

Go and get your 12v Battery checked, otherwise It's likely to be the fairly common integration relay issue

82641-74010

[mds33]

1 hour ago, Bper said:

Hi Mike,its possible that a malfunction is in the horn switch itself or the circuit. If the switch becomes stuck in the "on" position, it would continuously activate the horn, even when the engine is off and the ignition is off. This could explain why the horn stopped when the engine was started, as the power to the horn circuit may have been interrupted when the engine was running.

Replacing the horn switch may likely resolve the issue. I would also check the horn circuit for a possible short of damaged cable.Use a multimeter for continuity.Disconnect the electrical connector from the horn switch. Use the multimeter to check for continuity or resistance across the switch terminals while pressing the horn button. If there is no change in continuity or resistance when the button is pressed, the switch may be faulty and need replacement.Hope this helps

Thank you

[flash22]

I doubt it is the horn button as it only does it when the car is off

the horn relay (solid state relay) and fuse are part of the integration relay in the main fuse box - a drop in voltage can make the electronic go crazy (the Yaris can turn on its headlights) a faulty relay can have the same effect

 

the horn circuit is very simple