2021 GMC Sierra 3500 Engine Problems
- Complaints
- 3about this part
- Share
- 15%of 20 total for the year
- Median mileage
- —not reported
- Trend
- Not enough dataFewer than 15 complaints, too few for a reliable trend.
NHTSA recorded 3 complaints about the engine of the 2021 GMC Sierra 3500, 15% of the 20 complaints for this model year.
Fewer than 15 complaints name this part, so treat the figures as a rough indication only.
Example complaints
Selected from NHTSA records; personal details are removed. They are consumer reports, not findings.
“•The diesel exhaust fluid heater is a faulty component in the system, there is a back order on the part with no ETA • My pickup only does 55MPH right now and soon to do 5MPH you cannot drive on a public road doing 5MPH •There is thousands of other people having the same exact problem! •The DEF light is illuminated on my dash along with the check engine light, when you diagnose the error code it comes up with “P20C1 Reductant Heater C Control Circuit/OPEN””
NHTSA complaint #11454519, filed 2022-02“Multiple instances of diesel engine emissions system parts and software failure. While driving, towing or not, the DIC would randomly display a message that the DEF level is low and reduced speed will occur in x-amount of miles and that mileage would then begin a visible countdown on the DIC, sometimes much more quickly than the actual speed I was traveling. In other words, it might at first state 500 miles remaining, but then be counting down from 500 miles by one mile per second of time, or faster. …”
NHTSA complaint #11623109, filed 2024-11“The throttle body gets stuck wide open after the eninge gets up to operating temperature, it will give some warning with the throttle like on off throttle use and no codes show up at all. The risk of everyones is in extrem DANGER. The break are to soft and well not stop unless you put both feet on the break pedal down to the floor. Tranismission can NOT figure out what gear it needs to be in way too many gears and horrible fuel mpg for the 6.6L Duramax L5P. None of the GM dealership will look at the truck unless there is a code or it is happening right there when they look up the trucks VIN.”
NHTSA complaint #11455361, filed 2022-03Related service bulletins
- 11025492Nov 6, 2025Under Field Actions N252494000, N252494001, the service procedure includes performing a PICO test on vehicle engines within the identified suspect VIN population. If the engine…
- 11024330Sep 6, 2025This technical bulletin provides a procedure to replace the camshaft actuator magnet to correct customer concerns of engine related shudder.
- 11026017Jun 5, 2025This service bulletin provides information on replacing the intake manifold when the engine is replaced after severe internal engine damage.
- 11024486May 16, 2025This bulletin advises the tech to inspect deeper into what may be to main cause of an engine failure.
- 11024485May 15, 2025The service bulletin advises the tech of a normal transmission shift condition and the delay in throttle response when the throttle plate is opened rapidly and advises the…
- 11020254May 7, 2025This service bulletin provides information to dealership personnel for new vehicles with less than 1,000 miles that may not pass California smog inspection or smog inspection in…
- 11019503Apr 18, 2025This warranty administration bulletin provides policy information on vehicles outside of a California Emissions State who move to and register their vehicle in a California…
- 11017263Mar 25, 2025This bulletin advises the technician to flush the cooling system multiple times if oil has been found in the cooling system and replace the parts that may be contaminated due to…
- 11016945Mar 13, 2025This technical bulletin provides repair information to correct a customer concern of Evaporative DTCs P0442, P0446, P0455 or P0449, Caused by Dust Intrusion into the Evaporative…
- 11016942Mar 4, 2025This bulletin advises the technician to flush the cooling system multiple times if oil has been found in the cooling system and replace the parts that may be contaminated due to…
Engine: other model years
| Year | Complaints | Share of year |
|---|---|---|
| 2025 | 2 | 12% |
| 2024 | 8 | 16% |
| 2023 | 3 | 11% |
| 2022 | 3 | 9% |
| 2021 | 3 | 15% |
| 2020 | 6 | 12% |
| 2019 | 2 | 15% |
| 2018 | 1 | 7% |
| 2017 | 2 | 15% |
| 2016 | 5 | 26% |
| 2015 | 4 | 13% |
| 2014 | 1 | 14% |
| 2013 | 2 | 14% |
| 2012 | 3 | 33% |
| 2011 | 1 | 5% |
| 2008 | 1 | 4% |
| 2007 | 2 | 13% |
| 2005 | 1 | 4% |
| 2002 | 1 | 5% |
| 2001 | 2 | 6% |
Other parts of the 2021 GMC Sierra 3500
7 complaintsBrakes
5 complaintsElectrical system
4 complaintsOther or unknown
3 complaintsFuel system
2 complaintsBack-over prevention (rear camera)
1 complaintsBody and structure
1 complaintsTires
1 complaintsVisibility (wipers, defrost, mirrors)
1 complaints
← All problems reported for the 2021 GMC Sierra 3500
About this data. Data from NHTSA (ODI) complaints, recalls, TSBs and investigations, updated Oct 28, 2026. Complaints are unverified consumer reports and may be duplicated or inaccurate.
To check a specific vehicle for open recalls, use its VIN at nhtsa.gov/recalls. Methodology