Strange sound when engine shuts off

I have a 2014 Toyota Tacoma reg cab, 2wd, 4cyl automatic. There is a sound that only occurs for one second after engine shutoff. Describing the sound is hard but I guess it is like the sound of a wind up toy car if it was wound up and then let it free spin off the ground. Something like a whirling sound. I have owned two Toyota 4cyls before and have never heard anything like it. It only has 1K miles so I am thinking it could be something slipping because of the spray shine crap they coat the engine compartment with at the dealership. I have plenty of warranty but I was just wondering if I should bring it up when I take it in for free maintenance or if it was common with the 2.7, Thanks

 

Smog pump. Normal on all 2012+ tacomas.

 

Thanks, that's a big relief for me. I am really starting to like this truck. It's handy for all the activities I do and it gets great gas mileage doing it.

 

The pump only comes on for the first 90 seconds. It pumps any built-up unburned fuel into the intake manifold where it is consumed in the combustion process.

 

its the secondary air injection pump running a lil bit after you shut it off to help keep water out of the system
i work for toyota and thats what your hearing its normal
they had issues with the tundra burning up the pumps cause water got in them so they run after the truck is shut off to help keep the water out