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L5P RPM surge during decel

21K views 30 replies 20 participants last post by  JAE 
#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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#11 · (Edited)
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?
 
#9 ·
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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#12 ·
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...
 
#14 ·
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.
 
#15 ·
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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#17 ·
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 !
 
#23 ·
Because we all paid 60-70k for these trucks and it should not be acceptable that they are loaded with bugs. I and I can assume others have spent an giant amount of time in a gm service center to resolve this and other issues.

The worst part for me is that the ‘19 was a replacement for an ‘18 that GM bought back! I can only assume that Ford and Ram are no better.
 
#24 ·
hello My truck has being doing this since new and i have brought it back to the dealer several times. only truck i have ever driven that does this. its quite annoying. people look at you funny when its happening as it appears your reving the engine for no apparent reason.
Seems like GM doesn't want to acknowledge nor address the issue. hopefully some one figures out the problem.
 
#25 ·
Mine does it to. Has since about 1k miles. Over 70k miles now and still does it. Same cover up from the dealership for me. "We could not recreate the problem" then "GM corporate says this is normal". My truck surges aggressively. Nearly pulls the truck into intersections if I'm not quick and equally aggressive with the brakes. THIS IS NOT NORMAL GM. Fix this before someone dies! Imagine a woman pushing a stroller through a crosswalk and a big 3500 is first to the intersection and this happens to someone who's not quick on the brakes. It's on you GM because you think this is "NORMAL".
 
#26 ·
Have you checked/cleaned/replaced your MAP sensor yet?
My truck did this a couple times with a dirty MAP sensor.
 
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