Walked in on my Prime buzzing in the middle of the night

This happened to my gen 3 twice in the last month or so. I hit the power button twice (on position) without the brake and it stopped. I then turned the car off and it didn't come back. Same thing, sounded like it came from the area of the battery or the battery fan and it was louder on the outside than the inside. Not sure what it was either.

 

I don't know whether this would have any bearing on the question, but it might: Was it charging at the time?

 

Most likely the evap system test. Which is a noise from around the fuel tank. Happens after the car sits for a few hours.

 

Maybe the car did not like being walked in on.

 

this happened on both the old Pip, and a couple of times on the Prime.

I cannot figure out any rhyme or reason for it, but cycling the power switch turns off the noise.

It is not an evap systems test noise, because the steady buzzing will go on for a long time. I timed 5 minutes once and decided to power cycle and go upstairs.

 

Still sounds like a high probability of being the fuel evap test to me.

Per page 8 of the manual: "Approximately five hours after the hybrid system is turned off, you may hear sound coming from under the vehicle for several minutes. This is the sound of a fuel evaporation leakage check and, it does not indicate a malfunction."

 

I stand corrected.

Here's a vid someone posted with the evaporation test sound from a Prius C:

 

Yep that's it. That's the sound I heard. Maybe I shouldn't have stopped it then.

 

Now that I think about it, my 2011 Prius does that as well.

 

^ Vid... I have never ever heard anything like that from my 2010. That sounds really loud and annoying.

 

I have come to realize that we all are driving a computer that is never completely "off". It constantly checks itself, making sure that all systems are "go". The car is simply amazing, whether other (non hybrid-owners) want to admit or not.

 

This would be a good one for Coast Cruiser's Prius oddities.

 

You really don't notice it unless things are really quiet.

 

I'm shocked, only 788 pages and you couldn't find the time? I wouldn't feel guilty about that!

Seriously, this is getting out of control. They have what now, TWO quick reference guides included in the manuals pack? I definitely appreciate Toyota going to the trouble to document everything and I do hope they continue that level of detail going forward, however the level of complexity that cars are getting to strikes me as perilously close to beyond human scale at the driver level. The level of trust implicitly requested of end users of modern cars is growing by leaps and bounds...

 

Yeah, I just want it to get me from point "A" to point "B" without needing a PHD.