2021 GMC Sierra 2500 Engine Problems
- Complaints
- 8about this part
- Share
- 15%of 52 total for the year
- Median mileage
- 66,000miles
- Trend
- Not enough dataFewer than 15 complaints, too few for a reliable trend.
NHTSA recorded 8 complaints about the engine of the 2021 GMC Sierra 2500, 15% of the 52 complaints for this model year. Where a mileage was given, the median is 66,000 miles.
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.
“I am reporting repeated failures involving both the transmission and diesel emissions (DEF) system on my 2021 GMC Sierra 2500HD Denali equipped with the 6.6L Duramax diesel engine and Allison 10-speed automatic transmission. While under warranty, the truck required replacement of the aftertreatment fuel injector and later the Reductant Control Module due to DEF/emissions system failures. General Motors also completed recall-related transmission software updates on the vehicle. …”
NHTSA complaint #11746749, filed 2026-06“The contact owns a 2021 GMC Sierra 2500. The contact stated that while driving at 55 MPH, the vehicle stalled unexpectedly. There were no warning lights illuminated. The vehicle was taken to the local dealer, where it was diagnosed, and determined that the engine needed to be replaced. The engine was replaced; however, the failure recurred. While at a stop and attempting to drive around a curve, the vehicle stalled. No warning lights were illuminated. The vehicle was taken to the local dealer, where it was diagnosed with engine failure. The vehicle was not repaired. …”
NHTSA complaint #11728457, filed 2026-04, 77,000 miles“The contact owns a 2021 GMC Sierra 2500. The contact stated that the vehicle was equipped with an engine block heater that he plugged into the vehicle when the weather was below 32 degrees to start the vehicle. The contact stated that he noticed that the engine block heater was causing the GFCI outlet in his residence, to experience an electrical short circuit. The dealer was notified of the failure and informed the contact that it was a known failure. An appointment was scheduled for diagnostic testing. The vehicle was not diagnosed or repaired. …”
NHTSA complaint #11574476, filed 2024-02, 55,000 miles“The contact owns a 2021 GMC Sierra 2500. The contact stated while driving 40-55 MPH, the vehicle started losing motive power. The contact stated while pulling into a nearby independent mechanic shop, the vehicle started jerking significantly and stalled midway. The check engine warning light was illuminated. The mechanic diagnosed the vehicle with transmission failure. The vehicle was towed to the residence. The local dealer and several unknown dealers were notified of the failure and informed the contact that the transmission assembly was not available and could not be ordered. …”
NHTSA complaint #11631610, filed 2024-12, 134,000 milesRelated 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 |
|---|---|---|
| 2026 | 1 | 8% |
| 2025 | 4 | 14% |
| 2024 | 12 | 11% |
| 2023 | 3 | 9% |
| 2022 | 4 | 9% |
| 2021 | 8 | 15% |
| 2020 | 10 | 13% |
| 2019 | 6 | 19% |
| 2018 | 8 | 23% |
| 2017 | 6 | 16% |
| 2016 | 9 | 15% |
| 2015 | 7 | 8% |
| 2014 | 3 | 10% |
| 2013 | 1 | 2% |
| 2012 | 3 | 10% |
| 2011 | 5 | 8% |
| 2010 | 1 | 10% |
| 2009 | 2 | 6% |
| 2008 | 4 | 6% |
| 2007 | 1 | 1% |
| 2005 | 5 | 4% |
| 2004 | 9 | 6% |
| 2003 | 6 | 4% |
| 2002 | 2 | 1% |
| 2001 | 8 | 6% |
Other parts of the 2021 GMC Sierra 2500
13 complaintsExterior lighting
9 complaintsBrakes
7 complaintsElectrical system
6 complaintsBody and structure
5 complaintsLatches, locks and linkages
4 complaintsForward collision avoidance
3 complaintsOther or unknown
3 complaintsAir bags
2 complaintsFuel system
2 complaintsBack-over prevention (rear camera)
1 complaintsLane departure
1 complaints
← All problems reported for the 2021 GMC Sierra 2500
About this data. Data from NHTSA (ODI) complaints, recalls, TSBs and investigations, updated Oct 27, 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