Buzzing from under the frame with it parked?

My 2023 V6 SR5 is sitting in the drive. About 20 min. earlier (wild guess) I opened the passenger door to look at something inside and shut the door but didn't lock. I came back and heard a buzzing under the truck near the rear. Stuck my head under and seemed like it was coming from near the center of the vehicle but I didn't track it down completely. I listened for a minute thinking it would stop but it didn't. I peered inside and didn't see any lights on the dash but it was bright out so might have missed it. Opened the drivers door and it continued. Shut the door and after a short delay it stopped. Now I am very curious what it was. Seems like it could run the battery down eventually. Any idea what this is and why it was running?

 

Fuel evap check; completely normal (probably). Here's a bunch of similar threads to see if this helps confirm the sound you heard:
https://www.tacomaworld.com/threads...parked-not-running-2018.753086/#post-26832641

 

Thanks! Still weird. Especially 5 hours after you shut it off. Surprised I never noticed it on the previous 2015. Or maybe I did and forgot about it.

 

My 2007 Corolla did it as well. The buzz and the rare need to jiggle the steering wheel before startup to allow turning the key. Now I have push-button start ...

 

It happens occasionally. I've gotten used to the weird things these trucks do at this point. 7 years on no problems but I worry that all the new tech on 3rd Gen will come to bit us in the ass at some point.

 

Just the EVAP test running, 2nd gens do it as well. It's in the owners manual.

 

Yea, it is weird! truck just sitting there and starts doing stuff on it's own.
I hear it when i go out in my garage usually at night and after a fill up.

 

Christine ...

 

I heard something similar after filling up and parking at home. Few hours later I hear an odd noise coming my truck. I narrow it down to around the left rear side near the gas tank. Since the sound is kinda near the gas tank area I opened the gas cap and hear a whoosh of air and then the noise stops.

 

Grasshopper, don’t be fast to give answers in life. Slow down and don’t kill wonder in eyes of others. Have fun with ones who do not read owners manual.

 

Like the very first page. Hahaha!

 

Jim seems like a good guy. Zero posts about tires or lifts. I'll reserve the jackassery for those more deserving