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Discussion Starter #1
I purchased a brand new 2019 2500HD Duramax and at 1200 miles I noticed the engine surging during decel. When coasting to a stop from ~30mph (any speed as long as the transmission is in 2nd gear or higher when beginning the decel) when the truck is around 15mph, the RPM begins to surge 150-200 rpm. The RPM will continue to surge until the truck decels below about 12 mph at which time 1st gear engages and normal decel resumes. If on a slight downhill where the truck will maintain ~15mph, the surging will continue.

I brought it to the dealer and replicated the issue for them (now at 2200 miles and I can replicate the surge almost every time on decel). The dealer acknowledge this did not seem right. They ran their standard tests and did not find any issues. They then contacted GM corporate who took one of their vehicles and also replicated the problem on their vehicle! My dealership then took another truck from their lot and were also able to replicate the issue. Since all of the trucks had the same problem, GM claims this is 'normal' and is not an issue.

Has anyone else reported this issue? Can you go test your truck and see if you can duplicate the issue? If so, please bring it to your dealers attention. At the direction of my dealer, I filed a complaint with GM corporate to get the issue looked at further.

I'll post a video below if I can get it to upload. Thanks!
 

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Discussion Starter #2
Here is the video. Disregard the knocks you hear, those are due to phone movement. You can not hear the engine but you can see the RPM surge around 15 mph.

 

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If you had a monitor to see what actual gear you are in, you would probably see that it’s downshifting as you slow down. Mine does it too. Then at some point decelerating through 2nd gear and before it shits to 1st the torque converter unlocks.
 

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Discussion Starter #4
Correct, it is trying to downshift from 2nd to 1st. There is an error in their programming which they do not want to acknowledge.
 

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I have had exactly the same experience. My started right out of the wrapper on my first trip home. Enough of us with the issue need to make enough noise so that writing this flash becomes a priority.
 

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My dealership is outstanding. Plugged in and recorded as It was happening. It is up to GM to fix the code. The current explanation is minor fuel pressure fluctuation. I would not want to be towing down a grade and experience this.
 

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My 2019 does this also, but not every time. Have not taken it in for this yet.
 

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I’ve got at ‘19 as well with about 600 miles on the clock. I’ve noticed this, but it doesn’t stop me from slowing, or seem dangerous. Also, I broke the 1000 mile rule and towed my 12K lb fifth wheel a short distance in for maintenance. No issues slowing or stopping there either. I thought it was just the nature of the transmission working it’s way down. Looking at my monitor 2nd to 1st is most noticeable.


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Here is the video. Disregard the knocks you hear, those are due to phone movement. You can not hear the engine but you can see the RPM surge around 15 mph.

[/QUOTE

How come your coolant temp is so low?

If it's just that it hadn't yet been run long enough to warm up, then does it do the rpm thing with the coolant at normal running temp?


EDIT: I wasn't paying good attention to the video being an old post.

Is it still doing it?
In video odometer showing 1375 miles -- so possible trans was still learning?
 

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My 19 now has just over 40k miles and still doing it...dealer has contacted GM apparently and they claim to not know why. They don’t want to dig into it further because truck is outside the 36k bumper to bumper and don’t want to leave me with a huge bill...wtf. Hopefully GM offers an ecm update or something soon because it’s very annoying. Any one else having this issue? I can’t imagine it’s just a few 19 owners...
 

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Mine has done it since new. I'm at 10k miles. Clearly they're not going to do anything about it. I figured so, which is why I haven't taken it in. It's annoying, but not hurting anything I don't think.

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I have an 18 Duramax L5P and every once in a while (maybe once every month or 2) when decelling probably between 5-10 mph, it will downshift into 1st and obviously surge or throw me forward in my seat. I can't give specifics because I cannot replicate and it happens randomly so I'm not looking at the gauges when it happens (I'm in traffic so I'm paying attention to the cars in front of me 🤨). Is this what you're referring to or something else? I've written it off as a glitch in the programming but it is frustrating and would be alarming if towing and on a downhill slope.
 

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No, this is something else. It doesn't happen on a downshift. One way it does it every time is backing down my driveway. It's a little steep, and I back down fairly quickly. When I start slowing at the bottom, you can watch the tach bounce up and down by about a hundred rpm or so. And it will do it in first gear going forward too. Our boat is stored in a shed at the marina. It's up a steep hill. I give it almost no throttle to get rolling down the hill. It stays in first gear, but you can hear the engine surging a little and see it on the tach.

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Hi there, first time poster. I just purchased a 2019 L5p brand new off the lot last month. My truck does the exact same thing when I’m slowing dow to go to my mailbox on my way home from work everyday. I’ve already been going back and forth with my dealership about a rust issue on the frame so I’ve been waiting to get that dealt with before I bring this up. I will say a couple of times sitting at a stop light it has randomly surged but luckily when it’s happened my foot was on the brake pedal !
 

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Be sure to update this thread if they do something that fixes it. I'm sure a simple software update could take care of it, but it may not even be on GM's radar if there's not a lot of people complaining about it.

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Discussion Starter #19
I'll follow up with corporate next week. I haven't heard anything since filing the original complaint.
 
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