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2020 L5P Throbbing Sound While Idling

137K views 177 replies 48 participants last post by  Lane_32 
#1 ·
Just traded my 2018 2500 Duramax for a new 2020 2500 L5P and notice a throbbing sound at idle when the engine is warmed up ( currently 2200km). Dealership says it is covered under the #16-NA-32 Bulletin on common engine noises Duramax 6.6L, but this is not the ticking or cycling that I have heard on my previous Duramax. Has anyone else experienced this on the 2020 L5P?
 
#2 ·
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#4 ·
Yes if you increase the rpm the sound seems to be reduced or blends into the engine noise. Should also add that the sound seems to be deep in the passenger side of the engine
 
#158 ·
Thumping or knocking noise coming from what sounds like the rear of the engine. 2020-2021 6.6L 403 CID L5P #PIP5711A Duramax warm engine idle knock noise.
Characteristic noise being amplified by the transmission bell housing. This noise has no short or long term effects on the engine. Do not attempt repairs for this noise.​
 
#5 ·
When my trucks and machines are in "regeneration", the engine intake emits a thrumming sound. This goes for Cummins, Cat, and Duramax engines.
Could your truck be in "regeneration"?
 
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#6 ·
I don't think it is regenerating it has 2200 km on it and has been doing it since I took delivery at 60km
 
#8 ·
#10 ·
Have our brought the issue up with the Dealership? I have confirmed that the sound is not normal, other 2020 2500 Duramax do not have the throbbing sound
 
#12 ·
I recommend you do, the Dealership is going to take my truck into service and see what they can find out I will post the results when they have completed their inspection
 
#14 ·
That would be good news mine is currently being evaluated by the service department at the Dealership. However recently encountered a louder throbbing sound after a 2hr trip at highway speed it certainly gets worse when the engine is at running temperature.
 
#16 ·
Thanks for your response. The question is do all the 2020 L5P Duramax engines make this throbbing noise after warm up, my understanding at this point is that all 2020’s do not make this noise. I still look forward to the Dealership’s and now I understand GM’s response regarding this issue. I will keep you posted on how this issue is resolved.
 
#17 · (Edited)
The DURAMAX L5P 2017-2020 engine hasn’t basically changed so the 2020 shouldn’t develop new sounds from what people have reported from the previous years
The engine itself has changed part numbers every year for the last four but I don’t know what the exact changes have been made.
 
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#19 ·
The Dealership ran tests on the truck as requested by GM (disable each injector. ran with belts off) the noise persists. GM has acknowledged that some(not all) of the 2020 L5P Duramax engines are making this noise. They have requested that the vehicle be driven to the first oil change then inspect the vehicle to see if the noise goes away.
 
#20 ·
Yes mine has the same sound. It is odd though as I can hear it but a friend of mine with better hearing than me can't hear it.
 
#21 ·
My 2020 AT4 does the same thing... My 2017 didn't do it. But there are a few things that have changed in the engine bay, including placement of certain components...so the 2 trucks are not quite the same from a powertrain perspective.
 
#22 ·
That is my understanding as well, I am hoping that GM is continuing to look into the issue and will come up with a satisfactory solution. The last contact I have had with the Dealership was on November 27 as I outlined in my previous posting. I assume that other 2020 Duramax owners who are experiencing the same problem will bring it to GM’s attention as well, hopefully with some meaningful response.
 
#25 ·
So time for an update, my 2020 Duramax now has 6600km on it. It had the first oil change at 5500km the Dealership took oil samples and has listened to the noise which has now gotten worse (it now is a definite knock both at idle and at increased rpm). Still waiting for any response from GM regarding the problem, the Dealership has advised me that they are also concerned with how loud the knocking has become and are continuing to bring the mater up with GM.
 
#27 ·
Currently my 2020 Duramax has 7900km on it, the thumping noise has escalated to a definite knocking and now can be heard at higher RPM. Brought the truck into the Dealership last week for the tensioner recall and they wanted to keep it to deal with the engine knock. They later advised that they had ordered parts to repair the injectors that will be in first thing next week. I am hopeful that they can correct the problem and will update this thread as soon as the repairs are completed.
 
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