08 yukon momantary stall and high rev

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08-19-2016, 10:31 AM

jimr5454

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Join Date: Mar 2014

Posts: 156

08 yukon momantary stall and high rev

my 08 yukon truck at 177000 miles has started to do 2 things one is that at first when taking off from a stop it has a high rev and the goes like the first gear is slipping and other time it is starting to learch forward when slowing to a stop also the second issue which im think is unrelated to the first is when i turn the air on not always but more and more is starting to make a winy sound and goes up with the rpm and down with rpms the air temp is affected as well when the winy is going on the air is much cooler .right now i turn the air off tehn on again then the sound sometimes dissaperes but less and less lately .

no codes yet

08-26-2016, 10:13 AM

PRYUKON2008

Join Date: Dec 2013

Location: ROCKFORD, IL

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Re: 08 yukon momantary stall and high rev

My yukon has been doing the exact same thing for about 2 years now I'v taken it the dealer about 3 times and each time they can't duplicate the problem. It does it at least 3-4 times a month, but besides that no other issues. I have 180,000 miles and I think it started the learch thing at about 160,000 miles.

09-06-2016, 05:07 PM

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Location: Moreno Valley, CA

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Re: 08 yukon momantary stall and high rev

Quote:

Originally Posted by jimr5454

Typically you aren't going to see any codes with the known issue when these designed vehicles begin their intermittent lurching problems. The closes to a service bulletin that I could find on the internet was the following link (which is also the first quote below), http://www.autoserviceprofessional.c...brid-bump-jerk

Quote:

TSB's: GM hybrid bump/jerk
Posted on December 5, 2014 by Information provided by motologic.com
This bulletin applies to a number of GM hybrid vehicles, including 2009-2011 Cadillac Escalade, GMC Sierra and Chevy Silverado, and 2008-2011 Chevy Tahoe and GMC Yukon, all with two-mode Hybrid option RPO HP2 and 2ML70 transmission RPO M99.
Customers may comment on either of two drivability concerns. Bumps, jerks and/or surges caused by the auxiliary pump which occur during a transition into, out of, or during an Auto Stop, as observed on the tachometer.
A lull (clutch slipping) followed by a kick (clutch grabbing) during acceleration while in Auto Stop or during a transition to Engine On. This condition typically occurs just before and engine restart is observed on the tachometer.Surge or lunge during deceleration below 25 mph with light to moderate braking. This typically occurs after the tachometer drops below idle speed to anter an Auto Stop. These concerns may be caused by an auxiliary transmission fluid pump concern or a slipping clutch within the transmission.
NOTE: There may also be audible indications of electric motor speed increases and clicking noises associated with the auxiliary transmission fluid pump stall.
This concern is often accompanied by DTCs P2797, P0C2B and/or P079A. However, due to the intermittent nature of such complaints, there may be no DTCs set and reproducing the complaint can be difficult.
1. Check all vehicle modules and address any DTCs that may be present except for P2797 or P0C2B.
2. Once other DTCs have been addressed, obtain the date code of the auxillairy transmission fluid pump control module (this is found on the side of the module opposite the fluid hoses).
3. Follow the standard P2797 and/or P0C2B diagnostic procedures in order to diagnose the root cause of the complaint.
4,If the P2797 and/or P0C2B procedures do not identify either the auxiliary transmission fluid pump control module or auxiliary transmission fluid pump fault and the complaint is re-produced during those test procedures, inspect the :Hybrid Low, 1-2 clutch” assembly. Concerns relating to the “Hybrid Low, 1-2 clutch” assembly, typically manifest as a P079A DTC, but may not set the DTC.
5. If the concern does not re-produce, the “Hybrid Low, 1-2 clutch” assembly is operating normally and the control module has a Date Code of 089-11-XXXX or older, replace the auxiliary transmission fluid pump control module.

Quote:

Originally Posted by PRYUKON2008

There have been only a few reports on this forum that I recall that has gone through similar lurching type issues that also experiences a number of other almost un explainable issues such as engine RPM flare-ups anywhere from 2000 - 5000 RPM 2000 being more of the normal, gear slamming as if you did a N to F high rev shift so you hear and feel it both at the transmission and rear differential, (on a few rare occasions for ours) the SUV wanted to drive in reveres while taking off from a stop light, no engine power at times too....Plus a few other issues that escapes me.

While I'm still very intermittently experiencing some similar issues after having the Auxiliary Trans pump control module replaced still just under warranty for ours time wise with an updated design module and new wiring harness that fits an 2009? or 10+ Hybrid like described in the quote below, Our Hybrid seems to be running about 70% better now with most of the high number of issues diminished and we're in the process of trying to figure out the remaining issues that still seem related to the GM auxiliary transmission control module at least to me it does but not positive yet.

While I personally haven't tried unplugging the auxiliary transmission control module wiring harness as I'm still sort of under warranty (Long story) I do believe that what lt1gmc performed by unplugging the control harness may resolve many of the issues related to the lurching these vehicles seems to eventually exhibit....Best of all it's free to try to see if it helps any and shouldn't harm anything.

Here's my theory of why this may work. The control module is a computer, eventually almost all computer freezes up at some point not limited to even your home internet router, when you call tech support, what's the first thing they have you perform?? They ask you to completely disconnect the power and antenna input line...8 times out of 10 that repairs the issue. I think the computer just needs to be powered down for a bit and restarted.
I'm a boat service tech and we have one deigned ignition control module on the carbureted engines that has been know to very intermittently sound the overheat warning horn for no apparent reason, the only way to stop the horn is to unplug the ignition control module for a bit and all is fine there after....Thinking the same is happening here too.

Quote:

Originally Posted by lt1gmc

Didn't believe it was a battery problem as it runs on electric all the time and can go a couple miles on electric. Problem got really bad in the last couple of weeks, so I did some research: I found a tech bulletin about the auxiliary trans pump and or aux trans control module which described my issue perfectly. Problem is you have to use 2010 parts to replace either which require splicing the wiring harness as the new plugs/connectors are different. Also the module has to be programmed, removing this as a do it yourself fix. I decided to use my electrical trouble shooting experience and unplugged all the connectors and re-seated them. So far and 700 miles later no problems.

https://www.greenhybrid.com/forums/f...-hybrid-30812/
https://www.greenhybrid.com/forums/f...-system-30809/

If anyone happens to try disconnecting the Aux Trans Control Module, please let us know how it all works out for you here within this topic if possible. Thanks and good luck.