2017~2024 High Pitched Hum After Turning Off Ignition

[181962]

2020 CX-5 Touring AWD question:

When I turn off the ignition I get a high pitched hum coming from somewhere near the side of the engine block, hard to tell exactly where, right of the block when facing in toward the back...maybe. It goes for about 45 seconds then stops. I've only noticed it after the garage door is closed but since it is not very loud it might be happening every time and not that noticeable outdoors.

The manual mentions the cooling fan possibly running after shut down, as all modern cars do, but this isn't that and it doesn't get a mention in the manual.

Anybody know if this normal? If so, what is it doing? If abnormal, any clue as to the problem?

 

[cz5gt]

Yeah it's quite normal right after you shut down the engine. You can ignore it. It's not the fan although sometimes it can stay 'on' too.

 

[ruthrj]

I believe it’s the electronic power steering. My ‘13 does it as well and is completely normal.

 

[181962]

Thanks guys (or gals). After doing more checking around the most plausible answer is the direct injection system is running some kind of diagnostics with the sound coming from the high pressure fuel pump. Evidently this is a trait of Mazda direct injection engines across models going back several years. Normal, yes. I bet this has been covered in this forum numerous times, but when I did a seach on "hum" nothing came back. My appologies for the redundancy.

My 2015 Sienna issues a similar hum out of nowhere after the car has been shut down for hours. In that case, the owner's manual index has an entry for "Noise from under vehicle" pointing to page 24. In that "For Your Information" section it is explained that the vehicle is running a fuel evaporation leakage check about 5 hours after shut down, a kind of emissions check I presume.

A manual, a manual, my kingdom for a decent manual.