I have a 2012 GMC Yukon Denali that I bought in January of this year. When slowing down from an already slow speed, say going from 25 mph to 0 mph, the RPMs drop dramatically then come back up and then drop again. Usually it goes from 700 RPMs to 350-400. On two occasions the truck has actually died while I was slowing down. Here are a couple clues. It seems to happen when it’s hot, I always have my A/C on, and it gets slightly better after I’ve driven for a while - but not much better. “It’s under warranty, take it to the dealer!!” you might say. I’ve done that twice and since the check engine light hasn’t come on they say nothing’s wrong. They did clean the throttle body (truck has 9,000 miles), but that did nothing. They say when life gives you lemons make lemonade, I guess this will be a lifetime supply of lemonade. Any ideas on the problem???
The check engine light does not have to be on to have codes present. Offhand, it sounds like a throttle body/idle air valve issue or possibly a vacuum leak but the throttle body is not likely to need cleaning at under 9k miles.
Maybe it’s time to contact GM and drag them into this problem. It should be a warranty issue so you should document all of this in case this problem turns out to be a Lemon Law violation.
I agree with ok4450 concerning the Lemon Law. Make sure that you get a receipt every time you go to a dealer for any problem. If they can’t fix it, they owe you another, very expensive truck. The next time you get an unprofessional response about making lemonade (or anything else), ask to speak to the fool’s supervisor and make it clear that you do not like silly, unprofessional comments. You don’t have to threaten them with the Lemon Law. They know all about it. Do a web search for “lemon law” and your state to see what the requirements are.
I am not saying that you have a lemon, just that you need to be ready to get a replacement Denali if they can’t solve the problem. Be prepared to leave the truck with them and let a mechanic drive it for several days if need be to experience the problem. I think you deserve a loaner after dropping over $50,000 on their truck if you have to leave the Denali for a few days.
You do not have to have a check engine light or even any codes. You have a problem and they have to fix it. The check engine light is for emissions, you can have other problems that are not monitored by the OBDII.
Keep taking it back and keep all the documentation they give you. Do not leave without a repair order. Look in your owners manual for procedures to contact the GM customer service rep and do that. If it isn’t fixed in short order, then contact a lawyer for enacting the Lemon Law.
"...when life gives you lemons make lemonade.."..I break out the salt and Tequila. Lemonade is 'aight but I hate sweet drinks.
Seriously, I wonder whether this isn’t some sort of load condition. Most cars have a detector that senses electrical load and bumps the engine speed up a bit to accommodate for it. Maybe the voltage drops so much that it wants to stall. Of course, it is difficult to see what’s first: the stalling or the drop in voltage (classic chicken/egg problem) so I’d eek the idle a bit higher - not as a permanent fix, but as a method to see if it still wants to stall.
The dealer can’t figure that one out?
BTW, this will be an easy fix for them once they get motivated to fix it. They will also stop messing with you once they find out that you don’t give up easily. If you get a service evaluation form from them, do not be kind, but don’t make every mark the lowest or they will just dismiss it. The vehicle could turn out to be a great vehicle for you in the end.
All great suggestions. I’ve already contacted GM and got them involved. It’s frustrating when they say they can’t replace anything without codes. I bet if the truck wasn’t under warranty they would have replaced all sorts of parts by now. I’m going back to the dealership today, I’ll post my results (are lack there of).
silly dealer no codes go old school trouble shooting lazy techs
Is it possible this could be a weak battery? The 13s are almost ready to hit the lots and I have seen batteries fail in 18 months… These new vehicles rely heavily on the electronics at the proper voltages. Fuel injector pulse width (oops injector rise time) and all sorts of things are affected by a weak charging system. Has the tech even seen the truck exhibit the problem?
One thing I did was buy a cigarette lighter plug in volt meter. This was $15 at Walmart near the automotive section. I watched to see what the battery/electrical system voltages were during the issue I was having. Like RemcoW says, chicken and egg but maybe it will show you a very low voltage state or confirm it is not electrical. Plus it is a neat tool to see how the charging system works.
A good battery should be around 12.5V at rest, when you key on it will start to drop because of all the systems coming on line. When running it should be around 13.8V but can vary. My situation was showing near 9V at red lights and that was just too low. The battery would not pass a load test but only when it was hot outside.
You do not have to have a check engine light or even any codes. You have a problem and they have to fix it
Actually, first they have to witness it and verify it exists. Sometimes, with intermittant problems, this can be the hardest part of it. You can’t just waltz in, proclaim you have a problem and then after three attempts get a new vehicle. It’s frustrating for the owner but you have to be persistent and find a way to reliably reproduce the problem. Then go in and go for a drive with someone in the service dept to demonstrate the problem if necessary. Sometimes this level of involvement is necessary to get satisfaction.
silly dealer no codes go old school trouble shooting lazy techs
I’d be willing to bet dollars to donuts it has nothing to do with techs being lazy. Everyone I have ever met that works fixing things is all about solving problems. They would spend an eternity on something like this if they could until they solved the problem. The problem is, this is a business and they have to make money. The manufacturer isn’t going to foot the bill for a witch hunt. And the techs are marching to the company line on repairs…
I’ve been watching the voltage (as well as the active fuel management) looking for correlations, but I doubt the dash gauge is highly accurate. I may run to Wal-Mart and pick up the lighter voltage meter (sounds fun).
I have driven around with the tech and pointed out the erratic RPMs while slowing. Unfortunately it hasn’t stalled while doing this demo. The difficulty with trying to recreate an uncertain event with certainty is maddening, but expected by GM. I may mount a GoPro on my steering column (I’ve been looking for an excuse to buy one). The truck is back at the dealership now. Thanks for all the great tips.
@Twinturbo add to the fact that today’s vehicles are so advanced electronically, it takes a technician mind to reproduce a problem, correctly describe it to the service advisor and then hopefully it got conveyed with enough detail to the service tech. That doesn’t sound like the case here but a lot of symptoms are related to a completely different problem. Mine was no AC at stop light, turned out to be a bad battery. Go figure.
And the Go Pro is on my list of toys for the future also… I think they would be great for chasing down vehicle vibrations…
@mattedgar75, maybe you should suggest that the dealer buy some GoPros. They could solve intermittent problems faster and make friends out of customers.
Agreeing especially with the second paragraph in okay4450’s first comment here. Make sure you are checking your states Lemon Law procedures. I hear a lot of “Lemon Law” threats from people who have no idea, and only serve to be further miffed when they find out they don’t have even a small case.
Sounds like, though, you may be builing one for yourself. So, keep those documents!
It’s rare that I don’t agree with TT, but in this case I think it’s incumbent upon the dealership to put an event recorer on the vehicle if necessary. This is a brand new vehicle, this problem can and will happen in traffic, it IS a safety issue, and they need to go to whatever lengths necessary to diagnose it. Telling the customer to “make lemons” is totally unacceptable.
To the OP, I would suggest
- making sure everything is detailed on your copy of the shop orders
- keep your copies of the shop orders (it’s evidence)
- check into your state’s lemon laws…and use them if you have to
- follow up the chain to GM as you have been
- contact the National Highway Traffic Safety Association (NHTSA) and file a formal complaint. If this problem is common, and it may be, these complaints can cause a recall to be initiated, and then the manufacturer HAS to chase YOU down and correct the problem.
Let us know how you make out.
go here for your NHTSA search:
http://www-odi.nhtsa.dot.gov/complaints/
I didn’t see anything similar, but I just looked at the Yukon Denali and Tahoe from 2010-1012. You should also search the Suburban, regular Yukon, and Yukon XL…
TSM, the OP said this:
They say when life gives you lemons make lemonade, I guess this will be a lifetime supply of lemonade. Any ideas on the problem???
I don’t believe anyone from the dealership told them this, more that, in light of the situation, this was how the OP was going to approach it.
I don’t disagree with your assertion of what the dealer should do, only that it behooves the owner to provide a means to verify the problem exists so the dealership will admit there is a problem. Admitting you have a problem is the first step to recovery 
@the same mountainbike, just got back from the dealership and a data recorder is exactly what we are going to do. The lemon laws are nice to have, but in the event I don’t have a “lemon law case” GM still has an express bumper-to-bumper warranty as well as an implied warranty of merchantability (since driving probably constitutes ordinary use of a vehicle).
I also agree this IS a safety issue. In fact every time I speak with someone (live or on the phone) I emphasize how terrible it would be for all parties if my SUV died while turning in front of a cement truck. I like the NHTSA idea… A LOT (maybe I could put my tax dollars to work).
@W30post- I agree 100%
I haven’t taken any of my cars (or anything else for that matter) to a repair place in 30+ years but the few times I did, I wrote up a synopsis of the symptoms and what I had tried or noticed about the problem and left that on the passenger seat for the mechanic. You would not believe the reception that got from the service folks. People would come out to thank me for providing accurate details and helping them to quickly diagnose the problem. They would complain about the translation from customer to service writer to mechanic.
I’m not looking forward to the time I get so old I can’t fix my own stuff anymore and have to go back to paying someone else to do it…
Any updates on this?