After 2 and a half yrs, this noise is finally getting to me after a 3 day camping trip (2.5 yrs: that's how long I've had the truck). When you turn the engine off and remove the key, you get the
"beep boop, beep boop, beep boop" (I think it's 3 sets). It's pretty loud too. I know I didn't have this on my 96 or my 2000 SR5. Any ideas on how to
stop this noise? I've checked the owners manual, online and also used Yotatech's search.
Thanks much ! ( I have another minor annoyance but that will be a new thread)

 

Have you tried to figure out where the noise is coming from?

 

Have you checked for some reminance of a aftermarket alarm?
Maybe a bypass switch on the left side kick panel.

 

So, it looks like no one has this sound .....
To reply to the Q's:
1) Sounds come from the inside the vehicle, basically the dashboard area but can't pinpoint it since it's
kind of loud and doesn't last that long. The loudness is why I'd like to get rid of it but, full disclosure, I have
hypersensitive hearing probably.
2) There's nothing aftermarket about the vehicle at all; stock. That said, it makes sense that this has
something to do with the security system built into the vehicle.
I'll keep monitoring this post to see if anyone comes up with a solution.
thanks

 

Does it sound more like the dashboard/interior beep as in key in ignition, seatbelt, light reminder?
Does it sound like something out of the speakers? Does it happen with audio system on or off? Could it be something electrical, i.e., capacitors going bad in the audio system?
Or does it sound like the chirping of an alarm system?
Sounds like the chirp of the alarm when:
1) You forgot to do something before exiting the vehicle, OR
2) You come back to your vehicle and there was an attempt to open the vehicle while you were away...

 

Probably the stereo head unit.. Mine does this.

Is it a Sony?

 

https://m.youtube.com/watch?v=w9wMQx1PRxs

 

BINGO !!!! That is exactly it and the video link you sent is my stinkin' Sony unit and the sound is identical (I did not install this unit; came with the vehicle)

So, consider this problem SOLVED!
Thanks, CO-94 !!