Buzzing noise

Can anyone tell me why my truck will sometimes make a buzzing noise at night. It sounds like it’s coming from the gas tank area under the truck.
Is this normal?

 

Yes it's normal, it's the leak detection pump running for the EVAP leak check.

 

Tacoma gnomes. If you had left them alone they would have cobbled a new suspension for you while you slept.

But no. You went and noticed them.



... Or you could believe the correct answer above me.

 

Thanks for the explanation Dm93, I figured it was probably something normal but I didn’t want to assume and have my battery run down because I neglected something!

Rock Lobster …
they must know that I heard them working cause a new suspension has not been magically installed

 

Yea the test runs at around 3-8 hrs after the truck is turned off and lasts around 5-10 min, there's may factors to enable the test to run but that's the timeframe. Basically a little vacuum pump pulls a vacuum on the fuel tank to check for leaks, that's what your hearing.