08 Tahoe Stalling, Jerking

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Old 02-23-2019, 10:46 AM
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Default 08 Tahoe Stalling, Jerking

So I've seen this discussed before, but I think miy situation may be a little different. Occasionally, as in maybe 1 out of every 10 trips, experience a stalling or jerking issue when leaving from a dead stop. My issue happens when the engine is still running and not in hybrid/ auto stop. I'll push the gas and it starts to go but then nothing, rpms do not increase, vehicle slowly moves forward, then it's just back to normal. At normal cruising speeds this is never a issue, only at dead stops. I see other talk about the aux fluid pump, and control module, but since this doesnt happen in auto stop I'd assume those devices shouldn't be the culprit? I already replaced the throttle body as I seen other people suggest this. Any ideas?
 
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Old 03-01-2019, 04:35 PM
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Default Re: 08 Tahoe Stalling, Jerking

Mine did that when the hybrid battery got really weak but it also had a couple of codes POAC4 and POBBD that popped up. Do you have codes?
 
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Old 03-03-2019, 02:02 PM
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Default Re: 08 Tahoe Stalling, Jerking

No codes, and only acts up seldomly. With the cold, dont get much hybrid mode, but when it warms up, I get plenty of electric only driving, so I tend to lean away from a battery issue?
 
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Old 03-03-2019, 04:03 PM
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Default Re: 08 Tahoe Stalling, Jerking

I guess my first stop would be at my local auto parts to have them check the 12V battery under the hood, since it is totally exposed to the outside weather the cold could be zapping it if it is weak. The hybrid battery uses the transmission electric motor to crank the engine at around 700 rpm You will Not get a slow crank like we are used to on "regular vehicles".when the 12V gets weak (these things are special LOL) The 12V battery controls most of the vehicle modules and could cause some crazy symptoms though if weak.

On the Hybrid battery I have found from my recent research that as stated all over the internet the GM Two Mode battery management system is pretty hard on the modules and it will Not set any codes until the battery is in very bad shape. Does your 08 have the original hybrid battery in it?. I just changed mine out in my 09 with over 200k miles. I think that I could have driven it much longer as it exhibited very few symptoms but I wanted the old one out so I could do some testing plus I wanted the vehicle to drive like new again. i got part of my wish as i got the old battery on my workbench. As far as drive-ability there is not a huge difference, there is some but not what I was hoping for.

On your symptoms mine was doing exactly what you described, when starting from a dead stop several times whether in ICE or EV it just randomly would hesitate and then one time it did that and actually popped up the 2 codes POAC4 and POBBD they went away after a few drive cycles. To me not being familiar with the Hybrid system (I have only had the vehicle a few months) I just thought it was driving NORMAL LOL.
When the codes actually popped up on mine the only thing I could relate it to (that was different ) was that I had just used the rear power outlet to run an air compressor for about 10 minutes airing up a buddies tire. After I drove off and stopped down the road when I took off again it hesitated and the codes popped up. Might just have been a coincidence I don't know? Anyway you are at the right spot to research and figure this thing out.

I just completed testing all 40 modules on my old battery today (pretty excited about this) here is the spreadsheet it shows the overall average capacity of the modules at less than 25% of the rated capacity. Amazing that it ran as well as it did, I was still getting long EV mode even up over 20mph and lots of autostop action
Some modules towards the ends of the pack might be OK if reconditioned but I do not think anymore than a handful could be saved and even then they would still be just old worn out 10 year old modules. New batteries are almost impossible to find and cost an arm and a leg. It looks like all us GM Two Mode owners are pretty much stuck with doing wack-a-mole as long as we own these silly things.
 
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  #5  
Old 03-07-2019, 04:37 PM
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Default Re: 08 Tahoe Stalling, Jerking

My '08 155k mi, original battery has been showing the same symptoms in the COLD Michigan winter. Yesterday, It set off Service Brake, Traction, Stabilatrak fault on dash and has been acting up since. It stalled at a stop with engine running and had to put in park and try and restart. Lucky it did at a busy intersection! I also have the slow speed engine running shutter and I usually throw it in neutral and ride it out. I plan on checking, cleaning, replacing modules when it warms up here but trying to do and hear what others have to say and have done. Tonight I just plan on checking and cleaning 12V battery terminals just to eliminate that but wondering if connection at BCM could be an issue too..? Any help would be greatly appreciated..TIA
 
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Old 03-07-2019, 05:35 PM
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Default Re: 08 Tahoe Stalling, Jerking

You may have reached the end of life on your Hybrid battery at a lower mileage than I did.
Problem seems to be (from my limited testing) that 90% or more of our modules in these GM Two Modes are going to be degraded by 75% or more from original rated capacity and are past the point of being saved. I tried to recondition the ends ones in mine but just was not possible with the equipment that i have. You can buy used tested modules in the 30 to 40 dollar range bucks each so you will end up with at least 1200 bucks worth of replacement cost and still most likely only have around a 60% battery pack. It really is too bad that you cannot buy NEW replacement modules anyone with decent mechanical skills and some knowledge can easily replace these modules.
When I first started my quest I had purchased 6 replacement modules. I have attached a spreadsheet of how they tested out. They show around 60% of original capacity with my crude test method. keep in mind these are 12 and 13 year old modules. All this info is very limited in size of scope and equipment and I do not pretend to be any type of expert or authority (just an experimenter) so take it all with a grain of salt. I will have to say that if I had this to do all over again I WOULD find a NEW battery and pay the extra dollars and not even think about a reconditioned pack. Too late now for me.
 
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