Strange noise with truck parked and off.

Super excited just picked up my 2016 TRD OR yesterday. Drove the truck home last night and parked in my garage. This morning I walk out to the garage to get something and when I open the house door I can clearly hear a noise coming from the truck? The sound is coming from somewhere underneath the vehicle near the rear end. Before I could crawl under the truck to pinpoint the sound I opened the drivers side door and looked to verify the ignition was off (which it was). While I was in the cab checking this the noise stopped? I have not yet had the noise repeat itself but hope to get a video of it next time to post here. The noise sounds like an electric motor that is running/stalling (My first instinct when I walked into my garage was to open the garage door and check that my house AC condenser had not stalled), the volume of the sound is not exactly loud but in a quiet setting it is very noticeable (volume wise think smart phone playing music with volume about halfway turned up). My initial instinct with the sound once I realized it was coming from the truck was that it could be related to the power outlet in the rear or possibly the rear locker? What do you folks here think, has anyone else experienced this, or am I forgetting something silly simple?

Thank you

 

Normal noise in second gens. Probably same for 3rd. Its emissions junk.

 

Something with the EGR (exhaust gas re-circulation) system I think, it's been talked about here some in a few threads. Evaporative control or something like that....

 

Truck was off and parked overnight? That's not your truck making a noise .. lol

 

Awesome thank you for the fast responses!
To clarify the truck was off for over 8 hours before I heard this noise.
This is normal sound/noise after the vehicle has been off for over 8 hours?

 

Yes. This is when it happens. After a period of being turned off.

 

read the manual

 

My '15 howles farts whines and pops when shut off, then when off for hours, buzzes and farts. All unusual noises I hear from the ruck, I say they are emission related and carry on.

 

I actually read that sucker and don't recall anything about this particular sound. Granted, I glossed over a bit. if you could let us know where it is addressed, that might be helpful!

 

http://www.toyota.com/t3Portal/document/om-s/OM04005U/pdf/OM04005U.pdf

Page # 8 in the owners manual.

 

Excellent information guys. Sorry for the silly questions.
Thank you for the help

 

"Approximately five hours after the engine is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and it does not indicate a malfunction."

From pg. 8 of the Owners Manual.

 

Wow....just the other night i went into my garage and herd some noise did not think about it being from the truck and was looking all around could not find the origin. now this post maybe answer....

 

My 335d BMW (twin turbo diesel) makes all kinds of odd mechanical noises for 5 or 10 minutes after shutting off. Sounds like valves opening, vents closing, small electrical motors whirring....

 

It's the gremlins breaking more stuff.

 

Mine is quiet as a church mouse.

 

Modern cars can continue to operate their on-board monitors for several hours after the car is turned off. Its most often the EVAP system. It will monitor, release, and repressurize the fuel tank (via evaporation) with the car off. Its all to gauge what is the actual pressure change compared to what is acceptable.

 

I just did a transmission fluid change and I heard the same noise the morning after. It sounded like a fridge after you use the water spout. I freaked out thinking a broke my truck, glad to know it’s normal.