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2500HD/3500 HD Trucks & Drivetrain Discussion Forum for the 2001 & newer 2500HD/3500 Trucks, Transmissions & Drivetrain

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Old 12-19-2017, 11:15 PM
gary_lucas's Avatar
gary_lucas gary_lucas is offline
Join Date: May 2012
Location: Langley
Posts: 372
Default Tracking down an intermittent electrical issue / battery drain

Ok, further to this:

* Battery is dead or near dead after a few days.
* Passenger side door ajar messages comes on.
* Occasionally the alarm goes off.

But only when:
* It's excessively cold wet or snowy.

This happened last winter too, but I had so many other problems (The entire front end + head gaskets) that I kinda ignored it and just got in the habit of d/c the battery negative terminals.

I had assumed it was possibly a bad door actuator, but if it only happens in crappy weather I'm now assuming it's an electrical fault. I think it's the passenger side rear door.

Any thoughts on how to go about tracking this down? I assume the battery going dead is likely the BCM triggering / not being able to stay shut down. At this point the batteries have gone dead enough times I'm pretty sure their hosed but I don't want to put more money into batteries until I've fixed the root cause. This time around I put a charger on them for a couple of days and then d/c the ground.

GMC Sierra 2500hd 2004.5 now with ARP studs
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Old 12-20-2017, 06:38 AM
DieselDavy DieselDavy is offline
Join Date: Sep 2001
Location: Ft. Wayne, In.
Posts: 452

Is the actuator on this rig similar to those used on the '80s trucks? If so, those could be the issue. They were pretty cheep. I have no idea how these circuits work now, but I'd start by removing one of those door switches and check it. They used to apply 12V to the door switch and ground it when the door opened. It was easy for the switches to wet/rusty with time. This could cause the switches to "short out" and continuously drain the battery. In the old trucks, that would mean your dome light could stay and you'd notice it, but with today's trucks, the compuker will shut it off after 30 minuits anyway and you might not notice it?
It's probably more complicated than it used to be (why, because they can) so my advice may be useless!
Let us know how it turns out!
Dave, N9LOV
Member #242
Dave's Diesels:
Sold June, 07 '82 1/2 ton 4X4;340k miles
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Old 12-20-2017, 09:43 AM
Yukon6.2 Yukon6.2 is offline
Join Date: Dec 2003
Location: Yukon Canada
Posts: 1,044

Hi Gary
What i would try to narrow it down is...
After you have the batteries charged start pulling fuses till you find ones that have a draw.My way since in don't know much about electronics would be to watch for a small spark as you disconnect the fuse or reconnect the fuse.If you have a good tester you probably can test each circuit to see which one has a draw that shouldn't be there.
I know a guy who has a gasser of the same vintage that drains the battery's after a few days.His fix has been to disconnect the battery's.He only uses it to haul water and wood so i suggested putting in a battery disconnect switch.Not a fix but a workable solution for him.
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews
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Old 12-21-2017, 05:30 PM
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gary_lucas gary_lucas is offline
Join Date: May 2012
Location: Langley
Posts: 372

Thanks for the replies.

I think we know the BCM is being engaged, we know this because the alarm goes off + the DIC shows a passenger door open.

The battery issue is likely related, but I guess fix the obvious problem first and see if the other problem goes away.

I'm thinking it's either the lock actuator is faulty or (much worse) there's some short in the wiring between the BCM and the module. When I get some decent weather I'll probably see if I can confirm which door is throwing the error (rear or front). Then put a circuit test on the wire going to the BCM and see if it's showing correctly.

Need to do some more research.

One thing to note, the newer trucks do _not_ have a switch showing door open / closed. It's located IN the actuator module which is buried in the door :|

I did pull out the wiring in the hinge and take a look last year, it looked fine. I really, really hope the wire isn't shorting out somewhere along the run...

GMC Sierra 2500hd 2004.5 now with ARP studs
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