2011 Tahoe LTZ battery goes dead because of intermittent draw on battery

[LiteUrEyes]

so you traced it to the tcm?


I was going to say I noticed a weird thing in my 2011 that I've not seen anywhere else talked about. I had the after blow turned on, to dry the evap to keep from smelling moist all the time. you've probably heard of it working at a dealer, but it's supposed to turn the blower motor on for a few mins after you turn the truck off, well I was on a long road trip, and was going to catch a nap in the back seat. after a bit the blower came on, ran for what seemed like a normal amount of time and went off. it should only do this once, but funny thing after a while it did it again. and then a 3rd time. by then I was like man I don't wanna get stuck at a random rest stop by myself with a dead battery over this. so I reached up and cycled the key and it shut off.

have always wondered how many times it would have done that if left alone.

I've since turned off the afterblow setting and just try to turn the ac off before parking it. I have a steep driveway and the water doesn't drain out till I back out the next day. leaving a long water line and smelly air lol.

4amps seems low for a blower motor running. but just something it made me think of.


also there's youtube video somewhere that shows how to measure current drain across the fuses using voltage drop instead of trying to read inline current. I wasn't sure that would work till I had a Ford truck that was killing me and I went ahead and tired it. it lead to me to water getting in a bed light housing. craziness.

I'm not really sure about all you just said, it was a naked ground wire that went from the negative terminal. It had wrapped itself around other wires. They traced it out and unwrapped it. Still no more problems. That wire went to the block.

 

[swathdiver]

Hi everyone I'm new to the forum but am a retired GM tech. I have a strange problem with my 2011 Tahoe LTZ. The battery gets weak at times but the other day the battery was dead after sitting for 2 days. The AGM battery is 13 month's old and does recharge to full state. I preformed a parasitic draw test with my Fluke 87 multi meter on the amp setting and after the truck sat for 2 hours it read 20 milliamps with the meter in series but after another hour and the meter on min max it showed 200 milliamps on the high reading and went right back to 20MA. What the be causing this strange problem. It doesn't happen long enough to catch doing a voltage drop across the fuses. All doors are latched including the hood. I have been out of the dealer for 14 years so I have done what I can at this point other than buying a clamp meter but again I can't sit there for a hour just to see 200 milliamps come and go because the average is 30MA. Are there any bulletins out there that could explain this issue like a radio or radio amp or other module come on intermittently.

Does your truck sit for days at a time and then only makes short runs most of the time?

A bi-directional scan tool, like the old Tech-2 you used, can run a parasitic draw test on the truck. The charging system was not designed for AGM batteries. They will work fine generally speaking but not last as long as they could have in a vehicle programmed to charge them.

 

[Fless]

A bi-directional scan tool, like the old Tech-2 you used, can run a parasitic draw test on the truck.

It can? Pray tell, where to find that in the menus.

 

[Doubeleive]

ditto, never seen that option even out of all the times I was trying to figure wtf was going on with the rvg

 

[swathdiver]

It can? Pray tell, where to find that in the menus.

ditto, never seen that option even out of all the times I was trying to figure wtf was going on with the rvg

I'll have to pull mine out and look. Well, it's pouring out, reading shop manual says test is done with J-38758 which looks like it disconnects the negative terminal and is used in conjunction with a voltmeter to measure amps. In the BCM menu, there is a data parameter that lists parasitic current, maybe that's what fouled me up. My apologies fellas.

 

[Gearz]

Hi everyone I have narrowed the battery drain down to two circuits fuses 15 BCM & 17 IS LSP so when the two fuse are remove the intermittent 4amp draw is gone. Where do I go from here if it’s two circuits. I need wiring diagram’s for those circuits unless someone has had this same issue and has a fix? I was going to have the two circuit on a switcked ignition but thats removes keyless entry security etc…

 

[j91z28d1]

is that the fuse box at the left end of dash?

my diagram doesn't show the numbers, so I don't see 15 and 17 anywhere. but hopefully this is them.

if so, they run straight into the bcm.

 

[Gearz]

Yes that’s the left dash. Thank you very much but there is so many circuits on those two fuses I would need a Oscilloscope and monitor the high and low speed lan circuit. This is out of my league :-( I have unplugged so many modules and it has no affect that it might be internal BCM issue but it would be a expensive guess.

 

[j91z28d1]

yeah. am now sure where to go with that one either.

hopefully others have an idea. I got nothing

 

[mikez71]

Not sure if this has anything to do with it, but it mentions some areas where wires can chafe or terminals back out (since Gearz mentioned transmission and serial data line)

https://static.nhtsa.gov/odi/tsbs/2012/SB-10043829-6448.pdf