Why would you think radio is draining battery then? I’m sure it turns off. The power is cut off when you get out and lock car
As I have been struggling from this problem since beginning of this year but in short
I do have tested out individual circuits from the radio no drain found right-away and overall car battery drain when the car is locked is around 50-75milliamps which I believe is normal?
At one point the battery was replaced as well but was fine only for a month and then again draining issue started
The drain is sometimes when I don't drive for couple days or for a week or sometimes just after a day or sometimes If I have driven short distance.
I don't have any specific answer what causes the drain but these above are some scenario's
Later removed the radio fuse (33) from the fuse box and never saw any drain, tested for couple weeks without radio on. so definitely radio being the suspect.
I do see the radio get's off when the car is locked but my suspect is there is a possibility that the radio is trying to turn on or any particular wire is draining the battery randomly when the car is locked.