I got home form work last night at 5pm, turned off the car and went inside. At midnight I went out to the garage to take out the garbage and there was a whirring motor sound coming from the rear of the car. The car was off, the keys were inside the house but this motor sound kept going. It was not coming from the engine area, most definitely from the rear of the car. I looked at the dash and all the lights were out except for the one red light that blinks when the car is off. I tried cycling the power button but that did not stop the sound. So then I went and got my keys, and power cycled the car once again. This time the noise stopped. What was it?
Fuel vapour recovery system. The valves often "moan" when passing fuel vapour. I could say "RTFM", but that would be rude. But do so anyway.
It could be part of the Venting of the Gas Tank, Hybrid Fan motor, I hear them as well, in fact my S.O. told me the other day, that noises were heard 8-10 hours after I got home from work and as they were getting into their car in the Morning. I first thought...No, your crazy or hearing things, but I know it happens, just can't tell you what they are specificially. Some of the more "Techno Posters" I hope will explaing them because Now at least I feel normal....someone else hears them too! I do know they are "Normal"
This was no moan, it was a running motor or fan and it went on for at least 5 minutes that I was out there, and was already running when I went into the garage. Medium to high pitched whirring sound.
I don't know if the Gen III has the same system, but on the Gen II you also have a fuel system pressure test which runs several hours after the car is shut down. It makes the noise you describe. Tom
Just in case, make sure your gas cap is on correctly. If it were leaking air into the tank the pump might run longer than usual trying to clear vapors out of the tank.
On page-22 of owner's manual, it says... Noise from under vehicle after turning off the hybrid system "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." Ken@Japan
