H3 Dead in driveway - 3rd time now

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Originally Posted by Hunner

Way back there somewhere there was talk of the BCM and it being new or programmed to a specific vehicle. I thought it was a bunch of fuses and relays. Is there some ROM in there or something to program??
I also read about someone else installing the roof lights. I also had a problem getting the BCM to engage with the plugs under it. I found out how to lock them up before installing it. When I did put it in but not fully engaged I got all kinds of weird things going on. I wonder if that could still be part of this problem. If any one of those leads into those huge connectors is pushed out of contact or pinched and shorting to another one it could cause this. It could even be a shorted relay or one that hangs. It looks like installing a temporary amp meter in line with the battery would show if there was any drain while the system is off. I guess it would have to be a sensitive digital to be accurate. I would think the dealer would know what is supposed to be the draw on the PCM when off and maybe the alarm. Then check for any additional draw. Then of course it could be aliens. Do you park under large power lines are live next to a large deposit of iron ore?? It is probably a pulled stripped wire somewhere that would be good training for GM techs to figure out on there own time back in Detroit!! Sorry you are having this problem.

Ok, I'm confused.

All BCMs are programmed specific to a vehicle, the difference with the H3 BCM and most others is, once the BCM is programmed to the specific VIN, it cannot be reprogrammed to another VIN. So, the old trick of checking out if a BCM is failed on one vehicle, by putting in a known good BCM from another vehicle, reprogramming it, has been taken away.

As for current draw. I sure hope the dealer has performed a VAT test on the battery/charging/starting system to see if there is a larger than normal drain. All vehicles have a parasitic drain, but in most cars, the parasitic drain is higher for the first twenty minutes, then the controllers go to sleep, and the parasitic drain drops off.
If after twenty minutes, there is no excessive parasitic drain, then there is usually something wrong in the starting circuit or the charging circuit, and this can be check with a vehicle start (to see if the starter circuit is drawing excessive amps), and the charing circuit (to see that the charging circuit, including the generator is supplying the correct amps to the battery).

If all these tests check out, then there is a possibility that one of the controllers is waking up prematurely and causing a large amp draw. Extremely uncommon, but it can happen.

Battery failure is one of the highest warranty items facing any auto manufacturer, but this many batteries in one vehicle in this short of time, tells me that there is definitely a battery drain somewhere in the circuitry, and it appears that the dealer cannot find it or test for it correctly. My recommendation would be another dealer. If two dealers tell you there is nothing wrong, and you aren't leaving your lights on, then the vehicle is one of those very few that have an electrical problem that cannot be fixed. I have heard of them from other engineers, never seen one personally, but I guess they are out there.