Battery Drain Problem - 2008 3500 6.7

[wiley75]

2008 4x4, 6.7, G56, Laramie

My truck recently started pulling the batteries down to 11.5 volts after 4 days of sitting parked. Tried new batteries but didn't solve the problem

After unplugging the underhood light, alternator wire, trailer brake controller, and closing doors (unlocked, alarm off) I started a current draw test. My amp clamp shows that the electrical draw on the system hovers around 0.0 - 0.1 amps for 25 seconds, then 0.0 to negative 0.1 amps for 20 seconds, then jumps up to around 0.9-1.1 amps for 10 seconds. Then back to 0.0-0.1 amps again repeating the same cycle. It does this cycle continuously, over and over again. I watched it do this on my amp clamp for 10 minutes or so, then started pulling fuses one by one.

When I pulled fuse #11 the current draw indicated on amp clamp stayed at 0.0 to 0.1 amps (fluctuating). It never jumped up to 1 amp however. Plug fuse #11 back in, and it goes back to the cycle described above. Due to this, I'm pretty confident one of the components connected to the circuit on fuse #11 is my problem.

According to my owner's manual, Fuse #11 is for "Ignition Off Draw (IOD), Cabin Compartment Node (CCN), Radio, Under Hood Lamp, Wireless Control Module (WCM), Satellite Digital Audio Receiver (SDARS), Hands Free Module (HFM) EOM"

Two questions:
Where are these modules located? I pulled the glove box out and found two modules in there, but neither are labeled.
Any recommendations on what of the above listed components is the most likely culprit?

thanks very much
Wiley

 

[sag2]

You are lucky if it stays broken, makes it much easier to diagnose. This should help some with the locations.View attachment Dash modules 2008.pdf
The easiest way is to disconnect one connector at a time at the module and watch the draw. My guess is the cluster may end up being the one, but watch out, it isn't really the cluster. The most common problem was the lighting circuits that feed into the cluster. If the cluster sees a circuit request to turn on an interior light, it wakes up the BUS (the cycling of excessive draw, then normal draw) and a bunch of modules, then puts them back to sleep. If it goes away when you disconnect the cluster PM or answer and I will give you some more to go on.

 

[wiley75]

Thanks. for the info! I'll check into this. The diagram you provided is helpful. I'm not sure what all of the designations mean however. I presume to unplug the cluster harness I'd remove connectors C219, C220. Or perhaps C200 and C308? Hopefully I can get to all of these by just removing the access cover under the steering wheel and the glove box.

You eluded to something that compels me to share more of the story. When I took the amp clamp readings described in my original post I had the positive cable of both batteries connected. For the amp draw test, I removed the negative cable of the drivers side battery and kept the negative cable of the passenger side battery connected. I put my amp clamp on the negative cable of the passenger side battery. When finished taking readings as described I removed this negative cable, as the truck is going to sit all week and I wanted to prevent the batteries from dying until the weekend. However, I then reconnected said negative cable (passenger side battery) to check one last thing. When I did this and reconnected my amp clamp, the fluctuations had ceased. The clamp held pretty steady at something like 0.08 amps. So clearly something changed when I disconnected both batteries totally from the system, then reconnected. Hmmm. Perhaps when I cycle the key switch the cycle described in my original post will continue.

 

[sag2]

It is possible one of the modules reset and is not acting up any longer. You will need to get it with a consistent draw again to troubleshoot.

 

[Mingoglia]

Do you by chance have a MyGig radio? I ask because I had a 2008 Grand Cherokee SRT8 and my MyGig would stay on with the screen just barely visable. There was a TSB on this actually. I first noticed it after my original battery barely lasted a year, and then my second died just before 2 years. Turns out my radio appeared "off", but was staying on. Those radios have hard drives in them and probably pull more power than most radios. May not be your issue, but figured it was worth throwing that out there...

Mike

 

[wiley75]

Do you by chance have a MyGig radio? I ask because I had a 2008 Grand Cherokee SRT8 and my MyGig would stay on with the screen just barely visable. There was a TSB on this actually. I first noticed it after my original battery barely lasted a year, and then my second died just before 2 years. Turns out my radio appeared "off", but was staying on. Those radios have hard drives in them and probably pull more power than most radios. May not be your issue, but figured it was worth throwing that out there...

Mike

I don't have that radio. Mine is just the standard satellite radio with single disc CD. thanks for the heads up though

 

[wiley75]

It is possible one of the modules reset and is not acting up any longer. You will need to get it with a consistent draw again to troubleshoot.

sag2 - yep. I think that's what happened. I drove the truck around yesterday for a bit then shut it off and reconnected amp clamp meter as described in my last post. Sure enough, the fluctuations in amperage draw on the batteries have stopped. It'll no doubt start in again. I'll check it tonight to see what it's up to.

Sounds like I might be chasing this problem for a while

thanks

 

[sag2]

Now you will get a feel for what the dealer sees all too often. Bring it in and it fixed itself for a while. Once you get it again you need to jump in and start disconnecting modules. Be sure to wait a minute or two between modules for the BUS to react and go back to sleep after disconnecting any module. Leave them disconnected because when you connect it will wake the bus up for sure and may eliminate the problem again.