Fuel pump (?) running after truck is off

I have a 2019 TRDOR DC manual with the fuel pump recall installed and about 14000 mi.

I parked my truck in the garage around 2-3pm today. Went back into the garage around 7:30pm and heard something running. Some small motor or something, kinda sounded like an electric toothbrush. The sound came from the under the bed. Put the keys in and turned the battery on then off. The noise went away. Started the truck and it started fine. When I was driving today did not have any issues. After I parked the truck in the garage I was in there for a bit later and really don't think I heard anything.

Any idea what this is? Fuel pump maybe running? Should I get it checked out or just keep an eye on it?

Thanks!

 

Page 8, Owner's Manual.

 

ah, the ol' read the manual thing. Thanks!

 

Yes the old read your manual Technique.

 

I am amazed how many people are not curious.

 

As we used to say in the Army, RTFM!