Thanks Erica - I think we are making progress. The Dealership called this morning stating that they have located what they believe to be the problem. It appears that the transmission auxillary pump / module is likely the issue. The issue we are having is described perfectly in this TSB and once I got the dealership to stop saying this was "normal hybrid behavior" and listen to my concern...we are getting somewhere. Fingers crossed that this fixes it!

http://www.archivedsites.com/techlin...diagnosis.html

 

As a very interesting side note to others experiencing the same issue, the Auxillary pump is also on a GM "Parts Restriction". The replacement part must come directly from GM and the broken part shipped back for Quality to inspect it. This appears to be because GM suspects that a problem exists and is probably charging the warranty claims back to the OE manufacturer. Below is an explanation of the GM parts restriction process...

Parts Restrictions



There are times when Engineering will require the return of specific parts that have been replaced in order to analyze the issue with the part. For example, Engineers recently wanted to know why technicians were replacing the gas tanks on 2007-2010 Chevrolet Cobalt and Pontiac G5 models with the NU6 emission package. After placing a restriction on the fuel tank, GM Brand Quality found that the wiring harness was the source of the condition and the fuel tank did not need to be replaced, so the restriction was changed to only apply to the wiring harness.



In these instances, Engineering issues a PI identifying the component on “parts restriction.” When a part is on restriction, the dealership must report the condition to the PQC, along with documentation that supports the technician’s diagnosis that a part replacement is necessary. If Engineering agrees with the assessment, the required replacement part is authorized and shipped for next day arrival. The dealership must return the original part for engineering review.



The PQC team is working hard to help technicians fix vehicles quickly and positively impact the quality of GM’s products. The enhancements to the PQC process will help you get your customers back on the road faster while helping GM improve product quality.

 

beckel2013,

Please also read what evois has stated. The hybrid model engines are different. If you are trying to accelerate quickly the vehicle is going to switch out of the hybrid in order to switch over and give you the power you are looking for.

Erica Tiffany
GM Customer Care

 

I had a similar problem....it turned out to be a failed cooling fan on the battery pack. The motive drive comes from the electric system first and if the battery gets to hot it will cause the vehicle to not accelerate....very disconcerting! have your dealer check for battery overheating...there is a very specific process for doing this and if followed it will show up in the onboard diagnostics

 

Thanks Jet 1. I wasn't paying attention and did not know how that situation turned out.

 

I have to say I'm glad I found this thread. That link to the TSB described exactly what I've tried to tell the dealership, and have posted here before (2008 Yukon Hybrid).

Still have that intermittent hesitation issue, but I emailed the dealership that link today, and we'll see where it goes from here. Seems to me they checked that aux pump before.

If that can get solved, I might just keep the thing! It's the only nagging issue that's been there from the beginning. Still love the gas mileage for such a beast of a car, not to mention the 6L engine for power. Nearing 100K.

 

I'm also VERY glad I found this thread. I've had my '09 Silverado 4X4 Hybrid to the dealership THREE times for these same hesitation and surging issues for a few miles after startup. They never find anything. If the dealer can't find anything wrong, it must be my imagination, right? They give me the standard reply about "normal operating behavior" when I know it's not. I've driven the thing for 60,000+ miles. So now I can go back to the dealer (a fourth time) and provide them this information that they should already have. If this time it doesn't get fixed, I won't keep it past it's 100K warranty.

http://www.archivedsites.com/techlin...diagnosis.html

 

TIP: A low State of Charge (SOC) of the 300V battery may cause a similar jerk or surge condition. An updated minimum SOC of 60% has been established since a recent Emerging Issues seminar discussing the auxiliary transmission pump was released. Let the vehicle sit for one hour and make sure the SOC is above 60% before beginning diagnosis of the auxiliary transmission fluid pump.

Does this mean that the firmware is supposed to have been updated so that the minimum SOC is 60%, or just the the SOC needs to be 60% to diagnose? I tend not to get to a 60% SOC unless I'm going downhill, so it seems strange that this is the criteria for a test.

 

I have an 08 HyHoe with 82800 miles. The tranny has already been rebuilt. The vehicle has been doing more and more strange things recently.

When I go and start the truck after a day of work it often (a moderate temperatures) coughs. It then will not move in any gear for several seconds. You can push the accelerator and nothing happens. Then suddenly boom it remembers what you've asked it to do and it shoots off. I've almost gone through a wall (saved by standing on the brakes). No codes. Dealer cannot find why it does this.

It now, for lack of a better term, sounds and feels 'wrong.' The drivetrain sounds more 'growly' and I can feel a more mechanical vibration through the accelerator pedal and floor. Again, dealer can find nothing. I've felt what feels like little 'slips' in power application while driving on the turnpike. No codes.

It does not drive in all electrical mode as far or as readily as it has. I have a very soft foot and I cannot tease the system to stay in electric mode as fast or long as before. No codes, no dealer answer.

Finally, the driver's seat has developed 'slop'. It clunks back and forth, rocking a bit. You feel and hear it every time you accelerate and decelerate and is quite annoying.

I love this truck but I have to say that I have yet to find a dealer that I can forge a bond with. This was such a low volume vehicle that I feel that the dealers are struggling when I bring it in.

 

what's your location?