Strange rear-end noise

I was camping in Canyonlands this past weekend. I had driven my 2018 Off Road over some fairly rough terrain (Elephant Hill).

I got back to camp 4:00. About 5 hours later I hear a noise coming from the rear axle area. At first I thought it sounded like a tire was losing air but as I got closer and crawled under the bed, it clearly wasn't the tire losing air but it sounded like an electrical motor.

I couldn't find what was causing the noise. It sounded electrical, almost like the fan that kicks on when a computer gets too hot. The truck was completely cooled off as I hadn't driven it in 5 hours. I decided to drive it down the road about a mile and when I got back to camp the noise was gone

It was the strangest thing. I have no idea what could have been making the noise.

Any suggestions? Is there any sort of electrical motor in the rear area of the truck that would have randomly kicked on 5 hours after it was driven?

Thanks for any help.

 

Normal. Emissions related, system test.

 

This is one long, elaborate fart joke, isn't it.

 

Gas evap system

 

with a name like that, and posts like those above, I truly have nothing to add.

 

Three packs a day, he'll smoke 'til he dies Spicy McHaggis, one hell of a guy.

I got nothing on you’re mysterious noise

Sure it wasn’t the clutch fan?