(Zip file with 2 sound files attached - Mazda2.m4a is clearer)
I'm hearing a high pitch whine that persists for about 30-45 seconds AFTER the engine has been shut off. Car was purchased brand new in Feb 2019 and I noticed this from day one but it wasn't nearly as persistent and went away within 5 seconds of shutting off the engine. Just last month I started noticing that it took longer than a few seconds to go away and now I can hear it while the engine is running as well.
The sound is coming from the general area at the back of the car.

 

Try to untight the fuel cap a little.

 

This is one weird suggestion that worked! (Thank you ). Did it have anything to do with the fuel pump?

 

Well, the whine came back...untightening the cap doesn't appear to be the solution for this problem. The noise is coming from the exhaust system roughly 3/4 of the way back, around the rear wheels.

 

There is a bulletin on fuelpump on some WIN´s the impeller in pump and non-return valve can be faulty, let dealer check it out.
Mine was replaced under warranty.

 

The whine is there during an long after I shut off the engine (20 to 30 seconds after) Doesn't the fuel pump shut off as well?

 

Yes pump shut off, but if non-return valve is leaking, the build up pressure i fuelline will leak to fueltank thru valve, whine sound.
If you, when you hear it, turn on the ignition without starting engine - i bet the sound disappear. (turn down radio and shut off aircon first)

 

Yes, the sound disappears. I'm surprised there was no recall. Thank you for clearing this up for me.

 

Yes, the sound disappears. I'm surprised there was no recall. Thank you for clearing this up for me.

 

Also see these tread https://mazdas247.com/forum/t/just-r...2#post-6755818