Parasitic battery draw leading to the BCM2 fuse circuit - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 2 (permalink) Old 08-20-2019, 11:00 PM Thread Starter
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Join Date: Aug 2019
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Parasitic battery draw leading to the BCM2 fuse circuit

Hey everyone! I’ve been having a parasitic draw on my battery in my 2010 Chevy Cobalt 2LT 2.2 liter with 152000 miles on it currently. I’ve narrowed it down to having something to do with the BCM2 fuse circuit but I seem to be having trouble figuring out exactly what it is that’s causing it. Basically this is what’s been happening. Lately my battery seems to be dying over a short period of time. At first it started out slow, I would have the battery on with the engine off for a few minutes and then I would have to jump it and remove the negative battery cable so that I’d have enough power to start the car. I had my battery tested at the dealer and it showed that it was good, 586 CCA and it’s rated for 600 CCA. With the engine on and the alternator going the battery voltage sits around 14.5 to about 14.7 and I can remove the negative cable while it’s running with no problem so it has a good strong alternator charging it. I’ve noticed that when I go to start the car, with the negative cable off (even overnight) the battery would sit at the normal 12.55 to 12.62 volts. As soon as I reconnect the negative terminal the voltage would immediately drop to 11.90 volts and of course the car won’t start so it appears to have a pretty gnarly power draw. I disconnected the negative terminal and put my multimeter on it to check the current draw and it has a steady 320 to 340 mA draw so I started pulling fuses from the inside fuse box (BCM) to find that none of the fuses nor the HVAC relay being taken out would have any affect on the power draw. I then moved to the under hood fuse box and found a drop in current when I removed the 40 amp BCM2 fuse. I may be wrong but I’m pretty sure if the BCM was keeping something on and I didn’t know then the draw should have went away when I pulled the correct fuse in the BCM itself. I’m not having any issues that point to a bad BCM but I do still have the draw. I’m thinking there might be some corrosion or something in one or both of the blue connectors or maybe in the red part where the wires connect into it and has that bolt holding the wire housing in. Has anyone else had this issue? Is there a ground for the BCM that could be dirty or loose? Could it actually be that I need to replace the BCM? The only issue I’ve ever noticed tracing back to it is the fact that there’s a current draw somewhere on its circuit. Any advise or thoughts are much appreciated!
Devin.alex is offline  
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post #2 of 2 (permalink) Old 08-28-2019, 05:12 PM
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Join Date: Dec 2016
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I've read (AAA junk mail) that an 'electronic key' stored too near a car can drain the battery.

Also, if bought used, have you checked for aftermarket devices? (eg, remote start?)
ge315 is offline  
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