Noise coming from this location.....

I have been under my truck all morning running my wiring for my air compressor. Drove the truck this morning and it has been sitting for 5 hours. The only other thing I have done is swap out the spare for a 265/70R17 from an FJ. This spare is closer in size to the 275's I'm running than the factory spare was. Anyhow I crawl back under truck and hear a humming coming from this location. It is next to the fuel tank near the rear of the truck. I cycled the key and it shut off. Is it the fuel pump staying primed? Thanks for any help. I am sure it is harmless just curious.

 

Completely normal. System runs self check. Also runs self check after some numbers of hours of being turned off, it looks for leaks. Warning is in your owners manual.

 

Evaporative system check. Normal...

 

Very cool! Thanks for the info and quick replies

 

Ha ha, i thought this was strange the first time it happened to me as well.