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rendezvous help
10-16-2017, 02:03 PM
Post: #1
rendezvous help
My wife has a 2002 buick rendezvous cx. 6cyl auto. Its been having a starting issue. There are times it just wont start. It cranks each time. And there are times that if left alone for several hours or a day it will start no problem. The strange thing is if i put a set of jumper cables on it and jump it off another car it will start. I have discovered a parasitic drain on the battery and have used my multimeter to determine that its one of the bcm fuses. Now my question. Does a replacement bcm have to be programmed by a dealer?
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10-16-2017, 11:34 PM
Post: #2
RE: rendezvous help
A new BCM will be vehicle specific and will require programing because it stores things like the odometer reading and must also see certain options that are specific to that vehicle. Some even have the VIN in storage.

As a side note, if you can find the exact car in a scrap yard with all of the same options, you may get lucky. (had reports of that working) I haven't priced a new one so not sure what you'd save.
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10-17-2017, 06:25 AM
Post: #3
RE: rendezvous help
Another question to address is whether it is really a bad BCM. How much is the drain? I am pretty sure that even a good BCM draws a small amount of power at all times? Rupe? Do you know the answer to that?

Thanks for using the forum,
Garner

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10-17-2017, 09:49 AM
Post: #4
RE: rendezvous help
Normally the BCM draw is low enough (a few milliamps) that it won't drain a batter for a month or more but sometimes they do. I have also seen this with an ECM, but not in years.

The hard part with sorting out a BCM is waiting the 3-5 minutes after you think everything is off (doors closed, keys out, etc) so the BCM has finished it's cycle of timing out for all things that are on a delay. Also, if you have an alarm system that automatically arms, that will show a draw. Again, that should be low enough to not drain the battery for several weeks.

Now that you have mentioned this, I'd be curious to know the battery resting voltage and cranking voltage when the problem happens. One would think there'd be a marked difference in the cranking speed with a jump start, which will be related to battery voltage... and on a 15 year old car there may be other problems lingering.... or as simple as a failing battery.
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