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Old 11-02-2022, 11:15 AM   #1
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Duramax L5P Engine Failures

I am not suggesting that there is any problem(s) with the 2017 to current L5P Durmax Engines. I am curious owning a 2021 L5P myself if anyone has had any serious issues with this engine.
In doing research I find problems like NOX Sensors, DEF heaters / tanks, and injector electrical plugs, but that is about it.
Please let us know what your experience has been if you own a L5P equipped GM truck. I am not interested in opinions, or something you might have heard, only your experience as an owner. Thank you!
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Old 11-02-2022, 12:24 PM   #2
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Mine has been very reliable and 90% of its life is short in-town trips. I did replace a temperature sensor at the suggestion of owners on a Duramax site, and I have an Edge CTS monitor I use to keep track of temps, etc. I have no complaints yet.
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Old 11-02-2022, 12:37 PM   #3
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I purchased a new 2022 Denali 2500 diesel in March which now has 4600 miles.
No issues.
I love this truck!
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Old 11-02-2022, 02:18 PM   #4
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Originally Posted by BirchyBoy View Post
Mine has been very reliable and 90% of its life is short in-town trips. I did replace a temperature sensor at the suggestion of owners on a Duramax site, and I have an Edge CTS monitor I use to keep track of temps, etc. I have no complaints yet.
This is the part I replaced. When I replaced it at 36k the little cage around the sensor was gone.

GM ACDelco Original Equipment 12681993 Intake Air Pressure and Temperature Sensor
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Old 11-02-2022, 07:21 PM   #5
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Map sensor failure due to not using a winter front. Injector connector failure, cylinder #4, that caused a quite a ruckus.
3500 Duramax dually
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Old 03-16-2023, 03:56 PM   #6
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The L5P motor seams to be one of the most reliable Duramax's I have owned. They are work horses don't treat it like a 1/2 ton work it will last and get the job done fairly easy. Some guys buy these trucks as a daily driver and never work them and may not know how to maintain them.

the 2020 and early 21 trucks had a DEF tank heater issue that was fixed with a reflash and possible a tank heater and harness ( the connector burned up 2 pins at the tank ) . Mine has been fine now 2 winters since the repair by GM.

DEF , if your not working the truck your going to have a system with possible problems of clogged DEF injector.
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Old 09-17-2023, 07:32 PM   #7
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Iím having problems with my 2021 GMC 3500 DRW diesel, Nox sensor at first and now injector problems at 62,000 miles I had transmission problems but that was caused by the dealership.
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Old 09-24-2023, 07:20 PM   #8
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I have a 2018 3500HD that I bought used and in the 2 years driving it have only replaced both NOX sensors and the antifreeze reservoir because of failed sensor. Otherwise all runs and works we
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Old 10-02-2023, 12:01 PM   #9
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I have a 2017 3500 SRW SLT with 81500 kms. The issues I have had are:

- replacement of the coolant tank due to bad level sensor
- replacement of tranny cooler line due to rubbing on front bracket
- replacement of the block heater due to risk of fire (twice now so on the third one)
- replacement of glow plugs in #4 and #8
- replacement of side trailer mirrors - don't open/close when its cold out.

It is a solid truck and I am very happy with it but I do have a 2024 3500 AT4 on order.
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Old 10-20-2023, 05:45 AM   #10
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LML and L5P

2015 LML Silverado bought new, traded at 91000m. Def tank replaced 76000m
No other issues

2020 LP GMC 3500 Currently 81500m
Def head reflashed u/warranty, replaced radiator holding tank (leak) at dealer.

Both trucks bone stock; we are full time rvr's and tow 14k 5th all over the country. 70% highway miles the rest as daily driver. the truck is doing what it was built for, and does it really well.
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Old 11-30-2023, 12:45 PM   #11
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I just traded my 2018 Chevy DRW CC LB L5P for a new 2024 GMC Ultimate DRW CC LB L5P, I never had any problems with the 2018 and so far so good on the new one. Picked up Almost 1,000 lbs on the payload over the 2018.
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Old 12-05-2023, 04:02 PM   #12
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Bought mine used almost 2 years ago, only issues Iíve had were replacing the tires and getting the trailering app blanking out TSB software fix updated. Everything else has been fine.
2020 Chevy Silverado High Country 2500HD Long Bed CC 4WD Z71 Duramax
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Old 02-28-2024, 05:35 PM   #13
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I have a 2018 3500hd Duramax DRW diesel that I primarily use to tow my 18,000 GVW fifth wheel RV. Have not had any issues with it other than the occasional "check trailer brakes" or wiring....always has been an erroneous message. I think I have resolved that problem. I don't drive it around town when home. Have performed routine maintenance on schedule. Going to tow the RV to Alaska and back this summer. Love this truck.
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Old 02-28-2024, 05:45 PM   #14
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2019 3500 Dually replaced 2 glow plugs under warranty. Currently in shop getting #5 injector replaced. Not happy about injector issue
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