Now this is weird - car started with nobody in it

left it on by mistake?

 

bad 12 volt battery?

 

How?

 

when the sun spots are right, sometimes, when my neighbor closes his garage door, my car starts.

 

was it locked when it started?

 

Maybe it had started up sooner. Then it shuts down. And so on.

The "smoking gun" is that you left it on; think bisco nailed it in first response.

 

How did you know it was on?
If it was because you heard the engine, it is likely you left the car on.

If you leave the car on, it will sit there quietly until the traction battery runs down to a certain level.
At some point, the engine will turn on to recharge the traction battery. After it charges up some, the engine will turn off again and the cycle will continue.

 

When I first got my Prius I got out of the car and left it on a couple of times. What I started doing to prevent that is to lock the door every time I get out of the car and if it is left on the door will not lock and you will hear a loud audible sound that will get your attention that you left it on. It works for me.

 

I've done the same thing more than once!

Posted via the PriusChat mobile app.

 

i've left it on until i close the door and hear the beeps. i'm deaf, but i'm not that deaf.

 

...yet another reason to NOT disable all the warning/idiot lights!

Posted via the PriusChat mobile app.

 

if you look up idiot lights in the dictionary, you'll see my picture.

 

which would be a total bummer if your garage door was closed and carbon monoxide builds up.

 

Which is one of the reasons I like BEVs

 

It would be very difficult to build up a dangerous level of carbon monoxide with any modern car, let alone a Prius. Emissions systems reduce the CO output to essentially zero, even for conventional ICE cars. Now, I wouldn't bet my life on it, but that is what they say.

 

While this isn't common, it definitely does happen.
Poisoning death of Highland Park couple points to alarming trend - Lake County News-Sun

I would agree the amount of CO the Prius emits is much lower than that of a typical ICE car. But as you said, it isn't something you want to bet your life on.
More common would be blocked tailpipes. Such as from snow. Both are a small percentage of all CO poisonings, however some fear the numbers will grow as more and more cars move to key fobs.

 

On a side note, I always confound not only my wife, but the odd passenger riding shotgun, when, upon reaching my destination, I proceed to run a verbally animated "Vehicle Shut Down Check List" for my Gen II Prius . No, seriously. This is done virtually "Big Bang Theory" Nerd style . It's probably an OCD thing really, but it ensures that I don't walk away from "The Spaceship" with my propulsion system left online and operational. I've mentally programmed myself to accept that my Prius is a lot more than an ordinary car, so I tend to treat it the same way your average aviation pilot might treat his aircraft . Believe it or not, my Prius actually gets a 'preflight' walk around before I lift off, every morning!