I went out to the garage last night after my 2022 Prius had been sitting for several hours (after a short drive to the doctor) and heard what sounded like a small compressor running under the back of the car. I’m new to hybrids so forgive me if this is a question only to me, but what on earth was it!!???
Self-test of the evaporative emission control system. More info in this thread. Here's an illustration (but from a Gen 3 repair manual, some details might be different) of how the test works. The leak detection pump is what you hear.
Thank You! I looked here and in the repair/maintenance forums, never even thought of looking in the main one. You have relieved an old man’s worry!
