I noticed this last night and now tonight. I go out to my garage, and I hear this. It's sounds like a humming/ air compressor noise (not as loud, more muffled) coming from behind the driver's side rear wheel. It's a 2012 Prius V Pkg. 3. 162k mi. Going to try to attach a video with sound. The sound also goes up in intensity about half way though. What is it? Is it something I should be worried about?
Answer given by bisco in #2. A super-frequently-asked question around here. The owners' manual covers it: For the morbidly curious, another of the many threads where it's been discussed has a diagram of exactly what the car is doing in that test. You can see you might hear that pump running for as long as 22 minutes and change, depending on how long step C goes.
