After turning off engine, a high pitch tone from engine runs down the battery

Having the same issue, noticed a few weeks ago. three days in a row this week went out to a dead battery. Others with this have had bad solenoid, alternator or battery From what I can see. My battery tested fine, just weak right after we jumped it. Noticed tonight that thegear indicate light would not shut off wHen high pitch is present. I suspect the status light is what had been draining the battery. **update** It appears it was the gear status...the reason it would not go off is because it was not showing that the car was in park. I tapped the safety button on the gear shift, park lit up orange. Indicator light goes off and no more high pitch.

UPDATE: They could not find anything as a specific cause other than one cell in the battery was bad. However, it had tested fine two weeks prior. In any event, we put in a new battery and am hoping that resolves the issue. I don't have an answer yet, but have the same problem. The car is in the shop. I will post if I learn anything. Second time in the shop. They could not find an answer the first time.

I just wanted to say thank you for posting this as it is very helpful. Been having this problem with my car too and after a day and a half in the shop, they dealer could not find any problems with the car nor could they create the buzzing noise. I will try the gear shift and key switch, as I recall last time it was buzzing all night, I started the car, backed it out of the driveway and then back and it stopped. Just don't want another dead battery in the morning again!