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Have an electrical issue with my 2013 sedan M6 and electrical is definitely the weakest tool in my tool box. Battery is draining down overnight (New Battery) so I ran an amp meter between the negative post and the cable and it is drawing over 1 amps. I let the car sit for an hour before testing and made sure everything obvious was off. Started pulling fuses and relays in the trunk and under the hood and the only one that made a difference was under the hood, #36, which controls BCM 2, dropped down to 0.15 amps. Anyone know what BCM 2 controls? The only electrical mods on the car are the cutouts and the radar detector wired into my rearview mirror.
 

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Not certain but I believe that body control module controls the courtesy lights doors mirror trunk footwell etc. if you have a radar detector wired to your mirror I’d start there see if something is shorting out. Possibly the bcm is faulty?
 
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The BCMs control a lot of things, and are part of the communication path for the control of a lot of other things (they act like a hub, for example when the RFA says to unlock the doors, the BCM is what tells the doors to unlock). If pulling the BCM fuse killed the parasitic drain, the problem is almost certainly the BCM itself, vs. one of the other modules the BCM talks to. They're not outrageously expensive, but I think a replacement has to be programmed with your VIN which is kind of a PITA. A dealership would unquestionably be able to do it, but it won't be that cheap anymore...
 

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The BCMs control a lot of things, and are part of the communication path for the control of a lot of other things (they act like a hub, for example when the RFA says to unlock the doors, the BCM is what tells the doors to unlock). If pulling the BCM fuse killed the parasitic drain, the problem is almost certainly the BCM itself, vs. one of the other modules the BCM talks to. They're not outrageously expensive, but I think a replacement has to be programmed with your VIN which is kind of a PITA. A dealership would unquestionably be able to do it, but it won't be that cheap anymore...
That was my concern. I wonder if there is a way to test the BCM to confirm it is the issue?
 

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Just a thought, in my car in cold weather the door sensor would act up and cause the stereo and infotainment to remain on even after turning off the car and getting out. Dealer replaced both my door switches for good measure, no more issues. Probably nothing but FYI.


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did you retest after pulling?
I can remember trouble shooting years and years ago a different vehicle and my mechanic friend who is way better with these things mentioned something that you have the ( a ) door open that it will tell the car to turn the lights on and whatever else goes with it so of course you would get a draw
 

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That was my concern. I wonder if there is a way to test the BCM to confirm it is the issue?
Probably. But probably not without a Tech-II scanner.

Do you have a scan tool? The BCM might have been logging codes. If they don't interfere with emissions or safety, they don't light the Check Engine lamp. But there might be some errors that would help you zero in on something specific. Communication Loss errors or the like...
 

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I also have a 2013, sedan, 6-speed that has a radar detector hard wired. I have been trying to figure out why my voltage drops so fast, when parked.
It takes about 4 or 5 days to drop to around 12.1. I have the volt reading set to show up on the dash readout.
 

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These cars suck down a battery when they sit. Battery tender is a good investment if it’s not a daily.
 

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Have an electrical issue with my 2013 sedan M6 and electrical is definitely the weakest tool in my tool box. Battery is draining down overnight (New Battery) so I ran an amp meter between the negative post and the cable and it is drawing over 1 amps. I let the car sit for an hour before testing and made sure everything obvious was off. Started pulling fuses and relays in the trunk and under the hood and the only one that made a difference was under the hood, #36, which controls BCM 2, dropped down to 0.15 amps. Anyone know what BCM 2 controls? The only electrical mods on the car are the cutouts and the radar detector wired into my rearview mirror.
Did you figure this out, seems very similar to my drain issue
 

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Did you figure this out, seems very similar to my drain issue
I’d take a look through the V schematics I linked below but finding that fuse/BCM node would be rather painstaking. You’re more than welcome to look around in there, you might hit find that fuse and what it goes to. let me know if you need a second set of eyes.

https://1drv.ms/f/s!Am1HiCLFo3Gsm85wiX_2GqFeIenoew


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