When I turn off my truck, the horn automatically blasts. Any suggestions?

I turn the truck off. And after a 2 or 3 second delay, the horn starts blaring, as if someone were laying their body on the steering wheel. I then have to press the start button to stop it. There are probly other ways to stop it. But I know for sure that the remote does nothing, as I've mashed all those bottons, which did nothing. Had to walk back to the truck and press the start button to make it all stop.
All that to say, has anyone else experience this before? Any ideas for diagnosing or fixing it? I have no idea what is causing it. It just started today a couple hours ago, but hasn't stopped despite turning the vehicle on and off multiple times.
Thanks in advance folks.

 

You should probably call a priest, 'cuz your shit is clearly possessed!



Maybe disconnect the battery for a few minutes and see if it reboots whatever demons are living under your hood.

 

This gave me a much needed good laugh trying that now. Sometimes it only honks once instead of laying on it.

 

Check your battery connections and make sure they are clean and secure.
May not help, but it won't hurt..

On my 2005 the horn would go off every time I connected the battery..

 

All leads are clean and properly connected. I disconnected the battery for 5 min or so and hooked back up, but by that point it wasn't triggering anyways. And later it happened again. So that didn't fix it. Super annoying... Anyone have any other ideas

 

Does it have an aftermarket alarm or security interlock? I’ve seen those malfunction and cause gremlins like this.

 

As far as I know the auto start came stock on the 2020 Platinum, but it does have an aftermarket fob that has been paired with it. I haven't had any issues the past 6-8 months or so I've had it before that.. I did just check the auto start wiring. It's a STARTIT CM-DC3. Not sure if that's what Toyota uses stock or not

 

Maybe take a peak under the dash and see if there is any aftermarket device in there. When we bought my wife’s car it had some dealer installed “required for insurance” device installed under the dash. I promptly removed it as I saw it as a point of failure. It was tied inline with the start wires and a half dozen other wires under there.

 

Well I don't see any required for insurance thingy. A couple things that look odd, that tap into the auto start. But wires look intact. The only other after market mods I have on it , and that ive done, are spod 6 switch system and my amp steps that I put on like 9 months ago. Which the lights stopped working for them, but that's was months ago during winter. . . Idk. Maybe I'll just have to do some serious line tracing to see if something is crossing paths. Is there any sort of multimeter tests I can do that would indicate crossed wires? .. I couldn't find anyone with the same issue! Gonna pioneer my way through this one.

Infact now it for the first time went off randomly just before I fell asleep.
I'm reading that there's an issue where a hood latch sensor messes with something and sets off the alarm. But I wouldn't consider this an alarm... It's a horn blaring constantly. And to verify if the latch sensor is the issue, you can remote start, remote start won't let you under the hood if you try to start it, as a security measure, and will turn the vehicle off... Now, my vehicles auto start did stop working recently, starts for a few seconds and then turns off. Trys again and turns off ... Maybe related. Maybe not. For now I pulled the horn fuse under the hood. Will diagnosed more tomorrow night.