I had an issue a couple years ago with my battery dying overnight. After doing a little research, I decided to try replacing the FSR (Final Stage Resistor). A bad FSR will cause your HVAC to come on by itself, preventing the car from entering sleep mode. Not exactly any easy job because of where it's mounted, but I got it done myself, and it fixed my battery draw issue.

Good luck!

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2003 E53 3.0i
DOB 10/15/2002
Sienna red, Savannah Beige Dakota leather
Type FA53, Engine M54B30

2018 G02 30i
DOB 4/21/18
Black Sapphire Metallic / Canberra Beige Vermasca leather
Engine B46O