Strange electric motor noise when everything is off
 

My wife called me to the garage last night to investigate a noise which sounded like a small electric motor running. It appeared to be coming from the back of my Lexus. The car had been off for several hours and I have no idea what would be making the sound. Does this sound familiar to anyone? Thanks.

Nothing to worry about. It has something to do with emissions and is designed to come on after the car sits for 5 hours after driving it. Somewhere in the owners manual it will explain this. My 14 RX does this too.

The humming noise you hear coming from under the vehicle hours after turning Off the engine is the fuel evaporation leak check. Any time up to approximately 5 hours after the engine is turned Off, you may hear a humming sound coming from under the vehicle that could last up to several minutes. This is the sound of a fuel evaporation leakage check and, it does not indicate a malfunction.

Wow...interesting. Thanks guys!

To kind of piggyback on this, does anyone hear a click (sounds like something shuts off with a switch) after a few minutes of turning the car off? I usually park and then sit for a few minutes at work, and I always hear something click about 2 or 3 minutes in.