Hello! My check engine light came on yesterday. There is a constant buzzing noise coming from under where the air filter is. Any ideas what this might be? 2007 Prius Thank you.
You may be experiencing 2 problems. The check engine light could be emissions related (bad oxygen sensor or more likely a bad catalytic converter). But to pinpoint the problem, you just need to read the engine codes. The buzzing noise might be related to a failing ABS accumulator pump. This pump would constantly cycle if it's failing, stopping momentarily for a few seconds and cycle again.
You mean under the hood, under where the engine air filter is? That's the throttle body. It always sounds like that. There is an electric motor on it to position the throttle. The ECM sends electric pulses to the motor to control the position. It wiggles slightly with the pulses, which are at a frequency humans can hear, so you do. So that part is normal. (The buzzing JC91006 was talking about is a brake alarm inside the cabin, under the dash, and it's more like a long beeeep. If you ever hear that beeeep, you can tell it is the kind of sound made on purpose to warn you of something.) The buzzing of the throttle body under the hood is just the way that thing happens to sound. So none of this explains why your check engine light is on, but the good news there is whenever the ECM puts that light on, there are also trouble codes it will be holding for you to tell you why. Those just need to be read.
