Okay, so what is this

Went out to garage after parking vehicle 8 hours ago. I parked it unlocked with driver and front passenger window open, also back tail window open.

I go into garage hear a buzzing noise. Coming from rear around driver rear tire. then you can here it change tone.

It sounds like a fuel pump, I dunno

I did have key fob with me but didn’t touch the vehicle. I just heard it when I entered the garage.

It lasted until I started vehicle.

Went for a drive, parked it in garage

 

Fuel tank evap pump testing the vacuum system. It does it automatically after the car has been parked for awhile.

Totally normal.

I remember the first time I heard it, I thought the fuel pump was running even though the car was turned off.

 

Fuel evaporation leakage test.
https://www.4runners.com/threads/wh...h-gen-4runner-today.2261/page-414#post-203992

As they say, RTFM

 

Yep, a year ago, 2AM could not sleep, walked outside and heard "that" noise. Took a min to locate it and thought how weird. Bug? car running itself now? Skynet?
Used the net to find all threads discussing...Ok! normal operations. Yet, I still keep my eyes on the 4runner just in case it tries anything 'Arnold-like'. Personally, I figure it will be the garbage trucks with robotic arms that kicks things off.

 

Good to know.

Thanks