strange buzzing sound from my E83

I'm getting this strange buzzing sound from my E83 (2006, 53K miles) when engine is off. It happens when ignition is set to 2 (before starting the engine) and it seems it never stops when the key is at this position. If I turn off the car the sound goes away after a few seconds. What is this sound?



Somehow I think it's draining the battery. The car was complete dead this morning and when I drove to autozone after a jump start, they said the battery was fine but needs recharging. The battery was from Autozone a year ago and it's a Duralast H8-DLG.

No ideas put forward yet, so I'll try one.

Normally when the key is turned to position II there are a few things heard for several seconds.

I presume these to be servo motors energizing for heating and ventilation ducts, and maybe some other things such as the secondary air pump.
Similar buzzing sound to the one in your clip.

If they don't stop after a few seconds, I suppose there could be an electrical or mechanical issue with the offending component.

The fuse should provide fail-safe protection if something was stuck and drawing too much current.

In your case, it appears that it is not overloading, but just continuing to draw power when it shouldn't.

You might be able to identify relevant fuses to try pulling and narrow done the suspect list.

Check for buzzing also when the engine is shut down.
I have heard it sometimes but it does stop after 30 secs. or so.
Not the radiator cooling fan - unlike some other cars, I don't think ours continue to run after the engine is switched off.
But some other emissions control stuff might continue until their cycle is complete?

Thank you, Supercourse, for your reply!

Actually now I'm not sure if the draining battery problem is related to this sound. When I posted this I found that the TCU was not working properly. I made it work by resetting the battery. I found that many people complains that a faulty TCU can keep draining the battery.

The sound does disappear after I turn off the car (after a few seconds). So I assume whatever generates this sound is also shut off (hopefully).

I found one similar case that is giving a very similar sound. And someone says it might come from the idle control valve. Does anyone know where this valve is?

Thanks for the suggestion on the fuses. Yes I think that's a good idea. I guess I can probably just pull out the fuses one by one to see which one can shut it off. Is there any problem pulling out all the fuses (one at a time)?