I tried a search and didn't find anything about this. My car had been parked in our garage for several hours. I entered the garage and I heard something like a soft humming/whirring sound coming from beneath the rear of the car. After about thirty seconds, it stopped. I'm not concerned, since I suspect something is happening by design. However, I am curious as to what it might be. Any thoughts?
My HS used to make different sounds from the rear, like it was maintaining itself. I have traded it in on a 2013 ES300h that I had to special order to get all the options I want. I had the Tech package on my HS and wanted all the safety items it had on the new ES. Now I wait, they told me 3 to 4 months.