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?

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?

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?

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.

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

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.

Re: 08 Tahoe Stalling, Jerking
 

Is the hybrid battery the only thing you had to fix for this? I'm having the same issue with my 2008 Tahoe hybrid. I had those same codes and then reset the computer by unhooking the battery and now I have new codes coming up.

Re: 08 Tahoe Stalling, Jerking
 

Brittany Yes the Refurbished Hybrid Battery took away all the Hybrid system codes and it has done pretty well for a couple of years "knock on wood" I am at 257,000 miles now. .

That may be a separate issue on the Stabiltrak / Brake / ABS lights. Do you lose your power assist for the brakes when those lights come on?
When mine did that about 1 1/2 years ago I lost the braking power boost and it turned out to be a HydroBoost Pump failure. i have a thread around somewhere with a bunch of pics and other info, it might be on the Yukon Tahoe site though not here? if you are a member there? https://www.tahoeyukonforum.com/foru...discussion.79/
The Hydroboost brake assembly is a GM obsolete part so I had to purchase a used assembly and have it traded out and the system reprogrammed.
Cost a small fortune by the time I got through with it and I am not sure if it will last or not but so far so good. If you own one of these two modes you have to have tenacity and be tough LOL

Re: 08 Tahoe Stalling, Jerking
 

turn ff the Stabilitrak and traction control before shifting out of gear this will prevent the shuttering wait 3-5 seconds for it to shut off...



both can be turned off using the button below the radio (hold button to turn off both) then when your above 20mph it can be turned back on



I suspect if you still have the original AUX transmission pump it might be time to get another one (and an updated power supply to the 2010-13 one) they have a conversion kit (No wires need to be chopped up)


this converts the new connector to the older connection so the main controller does not have to also be swapped just the powersupply unit and pump

Power supply: 29547550 , (this one includes the new connector) :)


pump part # 19207983