electric whirring noise in rear of truck... after shut off !?

A little concerned about an unusual occurrence I just accidentally noticed...

Put my truck away in the garage when I got home from work around 3:30 this afternoon. (No mechanical issues of ANY kind prior to this.) Anyhow, I went out to the garage around 8:30 tonight to dump kitchen trash into a garbage can out there when I hear this distinct electric whirring motor sound coming from my truck. Which has been shut off for over 5 hours?!? I'm certain it was not making that sound when I climbed out of it earlier. (FYI - it was in 4WD if that makes any difference.)

So I walk around it... until I could pinpoint the sound as coming from the rear. Possible fuel pump or something? Fearing that something was left on (although I have no clue WHAT) and the battery was dying or getting there, I climbed in but nothing was amiss. I went and got the keyfob and started it up; no problem. Let it run for a minute or so and shut it off. Mystery noise was gone. Checked again about 45mins later and still nothing.

I'm worried now that it may happen again overnight and my battery will be dead in the morning and / or other possible damage could be done to other components of the vehicle. Can someone please tell me if they've had a similar instance as this and what in the world the noise might be, and why it happened? Is it possibly 'normal' and there's nothing to worry about? Maybe it's an automatic temperature-activated fuel line de-icing doohickey or some such?? (This truck has so many gizmos that are sci-fi techno hoohah to an old fart like me; my apologies if that sounded like a really stupid 'grasping at straws' guess.)

If nobody has any ideas then I've got to get my '17 TRD-OR to a dealership to find out. I cannot afford to damage anything nor am I able to go without my truck in the middle of winter for any length of time while costly repairs are affected. And I definitely don't want to blow this off only to have it die on me on my way to or from work or, God forbid, if there were some emergency and I were forced to be out driving during a blizzard or whatnot.

Please & Thank you!

 

normal, our subaru does this too. Has something to do this the gas tank evap i believe?

there's a thread somewhere on here specific to tacomas but it's the same deal

(All Years) - Noise coming from fuel tank area when parked? (merged thread) | Subaru Forester Owners Forum

 

check on it again at like 11 or 12. That might just be the truck doing its automatic emissions / evap stuff.

 

I think its some kind of emissions evap stuff

 

from the manual

 

definitely the evap. Freaked me out too one day out of the blue. Was also 5 hours later after parking the truck.

 

Thanks to ALL who replied and for allaying my fears. Now I can stop chewing my fingernails down to the first knuckle and just relax. Whew!

 

We were laying in the back of the truck, after dissolving some mind altering drugs on our tongues prior in the night. Trying to hide how terrified I was, so my GF didn't become panicked was one of the more difficult things I've ever done. That EVAP dance can be scary haha

 

we've all been there..