2005 Tahoe ABS

[nstahoe4]

Hi all. 2005 Tahoe with approx 140K on the odometer. battery kept running down and I found if it sat for more than a day or so it would drain. Then I thought it might be the Onstar/phone thing so pulled that fuse but didn't fix it. Did some googling and found some info on troubleshooting parasitic condition. I ran a M/M in-line and at first it wasn't working with my Craftsman meters. Turns out both had the 10A fuse blown, likely sometime in the past. Anyways, picked up a new meter and got to work. Sure enough I found the problem after just about pulling all the fuses - it was the ABS fuse and was drawing a pretty high number of mA. IIRC it dropped down to 30 or so after.

It's been out for a few weeks and no issues - except the dash light indicators. I've been driving it around trying to get the last monitor (evap) to finish and see if there are any other codes, but it is seemingly driving fine without ABS. I suppose I could just drive it as-is. If I decide to tackle it, can someone point me in the right direction for troubleshooting why the ABS fuse?
Thanks
Nick

 

[rockola1971]

Id be happy to help troubleshoot. Just in case it makes a difference is your Tahoe 2 or 4wd? Vin T, Z, or V? Was it the 60A ABS fuse that you found to have the draw? And to clarify the ABS circuit was showing 30ma draw on your ammeter?
The reason I am asking so many questions is typically its the BCM not going to sleep after the door is shut that causes the battery to run down overnight or so and that is caused by a corroded or busted ground wire behind engine or on the firewall or underneath drivers door on the chassis just behind the firewall line or in the drivers side pillar.
It is entirely possible you have a ABS fault which is causing your dead battery. I would also rule out the battery having shorted cells by fully charging it and disconnecting it from vehicle and see if battery can hold a charge on its own after being fully charged. Shorted diode in alternator will also run a battery down overnight.

 

[nstahoe4]

Thanks. I appreciate the response. It is 4WD with VIN T 5.3L.

The fuse I found causing the parasitic draw was the 60A ABS fuse. Unfortunately, I can't find the note I wrote the findings down on. I know precision matters here, but the draw observed was significant - something like ~300 - 400 (maybe more) mA and as soon as I pulled it, the draw went down to something in the 25-50 range which I read was "reasonable". My son was helping me so I can see if he remembers. I can also do the test again once I get the drive cycle finished to get it through emissions. I'm decent in the garage, but electrical isn't my strong suit.

 

[nstahoe4]

Forgot to mention the battery is fairly new and hasn't run down again since pulling the 60A fuse. I don't drive it regularly and it has sat for days. Turning 55 next week and starting to forget stuff. lol

 

[OR VietVet]

Welcome to the forum.

@nstahoe4, might want to post the rig info in your signature so that it always shows when you post. Just easier that way. That 30ma should be ok with a good battery. Like @rockola1971 said, when I am looking for a parasitic draw I always start with the alternator and go from there. Also, like has been said, that fairly new battery could have intermittent problem or even get some damage from repeated drains. Even though I also have an 05 and the same engine code and pay attention here to other like rigs, I can't think of a thread here about this ABS draw problem. I am gonna watch this thread, so please make sure to post back if problem is figured. You might also check all the threads here about doing "The Big Three".

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[rockola1971]

Forgot to mention the battery is fairly new and hasn't run down again since pulling the 60A fuse. I don't drive it regularly and it has sat for days. Turning 55 next week and starting to forget stuff. lol

Keep 60A fuse out and continue to monitor if battery runs down over say the next week. Its possible whatever was drawing down your battery just happened to stop doing it while you were troubleshooting. 300-400ma is less than 5w. It is also possible that the transistor inside the EBCM is partially shorting but I would think that if it were it would be turning on your ABS Motor since that is what the 60A fuse feeds ultimately. The transistor switches the ground on and off on your ABS motor BUT if your ABS motor were to short inside to ground then it would be bypassing your EBCM transistor switch and would draw your battery down.
My next test would be to stick 60A fuse back in and disconnect power wire directly from ABS motor....this is of course after ruling out a draw from the alternator and making sure that battery is fully charged for tests and holds a charge.

 

[nstahoe4]

Thanks for all the feedback and advice. I drove it today and was happy to see that it finally completed the drive cycle. No CEL so I'm happy about that and the fact that I can now bring it to emissions and hopefully get it through. Once that is done, I can do some more troubleshooting without worrying about disconnecting the battery, etc.

Signature updated. I have leather seats. Does it make mine an LT?

Nick

 

[OR VietVet]

Thanks for all the feedback and advice. I drove it today and was happy to see that it finally completed the drive cycle. No CEL so I'm happy about that and the fact that I can now bring it to emissions and hopefully get it through. Once that is done, I can do some more troubleshooting without worrying about disconnecting the battery, etc.

Signature updated. I have leather seats. Does it make mine an LT?

Nick

Many things are considered for the differences between LS and LT rigs. This goes in to great detail:

Difference Between Chevy Tahoe LS and Tahoe LT - Ask Any Difference

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askanydifference.com

 

[nstahoe4]

Thanks. I got it through emissions and know I don't have CEL, so I can do some troubleshooting. I'll start a separate thread if warranted on trim package and keep this one focused on ABS.