This isn’t a normal knocking noise, this is a noise that is made every once in a while. I have an 08 Prius. It sounds like something hitting the under carriage of the car. At first I thought it was simply a pinecone or something, but it’s been doing it randomly even when the car is in park. Does anyone have an idea as to what it might be?
Nothing specific in terms of known problem for this and usually people describe what they've done to investigate the problem before the ask us to help. Sometime people post a video of the noise but that usually doesn't translate so well unless it's a really bad noise. Random noises are not easy to diagnose in online forums, especially if your car is working without warning lights or other symptoms. Once you put more effort into searching for/better describing the noise, we might be of some use to you.
