Chevy and GMC Duramax Diesel Forum

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-   -   L5P RPM surge during decel (

lil_schmitty 07-29-2019 08:41 PM

L5P RPM surge during decel
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!

lil_schmitty 07-29-2019 08:54 PM

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.

MIkey52 07-30-2019 09:11 AM

L5P RPM surge during decel
If you had a monitor to see what actual gear you are in, you would probably see that itís 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.

lil_schmitty 07-30-2019 11:52 AM

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

mbroomhead 11-01-2019 11:22 AM

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.

FightinTexasAggie 11-01-2019 12:41 PM

Same issue here; replicated it at the dealership, waiting to see what GM says...

mbroomhead 11-01-2019 12:44 PM

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.

Collins 11-01-2019 04:47 PM

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

Boxer1200 11-01-2019 07:45 PM

Iíve got at Ď19 as well with about 600 miles on the clock. Iíve noticed this, but it doesnít 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 itís way down. Looking at my monitor 2nd to 1st is most noticeable.

Sent from my iPhone using Tapatalk

MIkey52 11-03-2019 12:33 PM

Looks like the truck saw a real hot Suburban.

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