Complaint volume
487 consumer-submitted complaints are matched to this model year. Treat the count as a research signal, then read the actual summaries for repeated symptoms.
Complaint records
2021 GMC Sierra Complaints
487 consumer-submitted complaints on record for the 2021 GMC Sierra, grouped by component category.
487 Total complaints
5 Crash reports
6 Fire reports
2 Injury reports
Complaint data reflects consumer-submitted reports. A complaint is not proof
of a defect, recall, or manufacturer fault. Enriched severity fields come
from official bulk records when the complaint can be matched by ODI number.
Buyer interpretation
How to use these complaints before buying
Complaint records are most useful when they turn into inspection points, seller questions, and comparison checks against nearby model years.
Pattern to inspect
The most common categories are engine, power train, engine and engine cooling. Use those categories as a test-drive checklist instead of judging the vehicle from the total count alone.
Severity flags
Enriched records include 5 crash reports, 6 fire reports, 2 injury reports, and 0 fatality reports. These fields come from complaint records and should be read in context.
Mileage clue
Mileage is available on 104 complaints, with an average reported failure mileage of 51,093 miles. Compare that with the mileage on the listing.
Questions to ask the seller
- Have you had any problems related to engine, power train, engine and engine cooling?
- Can I see recent maintenance and repair records?
- Has the vehicle ever been towed, involved in a crash, or repaired for the same issue twice?
- Can we also check the recall record for this 2021 GMC Sierra?
Used-car checklist
Use these complaints before the test drive.
Build a buyer checklist to turn these issues into questions and inspection points.
2021 GMC Sierra
Build buyer checklist Compare with other years Sends year, make, and model to pre-fill your checklist.
How severe are the 2021 GMC Sierra complaints?
5 Crash
6 Fire
2 Injury
0 Fatality
30 Towed
3 Medical attention
What are the most common 2021 GMC Sierra complaint categories?
ENGINE 156
POWER TRAIN 59
ENGINE AND ENGINE COOLING 37
POWER TRAIN,ENGINE 29
ELECTRICAL SYSTEM 26
UNKNOWN OR OTHER 14
STEERING 13
UNKNOWN OR OTHER,ENGINE 12
ELECTRICAL SYSTEM,ENGINE 9
SERVICE BRAKES 9
487 total complaints on record
Latest complaints
| Date | Component | Summary | Severity | Mileage |
|---|---|---|---|---|
| Apr 2025 | ENGINE | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, there was an abnormal sound coming from the engine compartment. The contact pulled over to the side of the road and discovered that the engine oil level was low. The check engine warning light was illuminated. The failure occurred on several different occasions. The vehicle was taken to a dealer, where it was diagnosed that the lifters needed to be replaced. The vehicle was repaired; however, the failure persisted. The vehicle was taken to a different dealer (Legacy Westbank Buick GMC; 3611 Lapalco Blvd, Harvey, LA 70058) to be diagnosed. The vehicle was not diagnosed or repaired. The contact was taken to a different dealer (Mossy of Picayune; 241 Frontage Rd, Picayune, MS 39466) where it was diagnosed that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 27,000. | Crash: No Fire: No Medical attention | 27,000 |
| Apr 2025 | ELECTRICAL SYSTEM,SERVICE BRAKES | ESC ERROR PARKING BREAK NOT RELEASING Dashboard lights started flashing Check engine light came on | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | at 16,000 miles Bank 1 lifters fail and replaced under warranty. now at 90190 miles Bank 1 lifters have failed again this time damaging the camshaft. I have all the service records for this engine and I was verbally assured by GM in 2021 that they would cover this repair until 100,000 miles. I know from looking on Google and talking with service advisors at GM that the 6.2L ecoTec3 V8 engines are having multiple problems related to my issue. GM should be able to warranty this engine to 100,000 miles and from past experience this engine should last 200,000 with good service. | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | Driving 75mph towing a 24' trailer and the motor just shut down and almost caused a massive pile up on [XXX] . INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Apr 2025 | ELECTRICAL SYSTEM | This truck, along with many others, has had wiring harness issues. My truck has fought this issue within the first six months of owning the truck. Since Jan 2025 it has left me stranded 3 times to be towed, and in the shop a total of 6 times for wiring harness issues. Rubbing that GM is 100% aware of how its designed. This has caused the truck to hesitate, shake, lunge, go in and out of gear severely hard then shut off while driving. All three time this happened to me recently i was on the interstate. GM has work orders out with all the codes and symptoms but wont do anything about it. Yes, i am out of warranty, but i am now paying over $5,000 for a new harness to be installed by a different dealer. The dealer that had always worked on this truck requested $8,100 so i called a new GM shop. This is a large issue and they keep turning their back and not addressing the issue and putting drivers at risk! Can provide last diagnostics and can request all notes from Stoops Buick GMC in Muncie Indiana, i have a rather large file there on this truck. | Crash: No Fire: No | Unknown |
| Apr 2025 | UNKNOWN OR OTHER | My tailgate will randomly open on its own. I’ve had several instances( 5 or 6 times so far) when I’ve had open on its own. Only once so far when i was driving. Luckily, i was on my private road without anything in my bed that could fall out. I often carry mountain bikes over the tailgate which could pose a serious danger if the tailgate were to open when driving. Also earlier this evening when the tailgate came down on its own while driving, when I got to my destination, I was unable to open the tailgate at all from outside the vehicle. It is apparent the button to release the switch is malfunctioning. I was able to get it to open by using release button inside the vehicle. | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | Driving on highway at approximately 70 mph and the engine completely cut off without warning. Error message on dash said put car in neutral and press the start button. After safely pulling over, the vehicle was never able to start or even crank. Towed back to the dealership. Catastrophic engine failure according to the dealership. Vehicle has the 6.2 V8 engine with known issues by GMC apparently. Only 32k miles and under warranty but dealership reports that replacement engines are on back order and they have not been able to source one. | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | Engine failure. Engine Locked up and truck shut down in the middle of the Freeway. Barely made it to the side of the road. | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | Lifter failure resulting in damage cam shafts | Crash: No Fire: No | Unknown |
| Apr 2025 | POWER TRAIN | Transmission will slam hard then truck goes into low power mode and doesn’t shift. | Crash: No Fire: No | Unknown |
| Apr 2025 | POWER TRAIN,ELECTRICAL SYSTEM,LATCHES/LOCKS/LINKAGES | The contact owns a 2021 GMC Sierra 1500. The contact stated while the vehicle was parked, the contact attempted to turn off the vehicle; however, the vehicle remained running. A message was displayed to shift to park(P). The contact stated that the lights, radio, and other functions remained operational. On another occasion, the vehicle jerked, and the steering was difficult to turn. The dealer was contacted; however, the vehicle had not been taken to be diagnosed or repaired. The contact also stated that the trunk failed to fully close. The message that the trunk was open was displayed. The contact attempted to close the trunk and message on the displayed was turned off; however, the trunk remained slightly open. The vehicle was not taken to be diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 63,315. | Crash: No Fire: No | 63,315 |
| Apr 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at 50 MPH, the transmission independently downshifted and the rear wheels seized. The contact stated that the rear wheels skidded. In addition, the contact noticed an abnormal clunking sound. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The dealer was made aware of the failure. The contact stated that the failure occurred immediately after the recall repair under NHTSA Campaign Number: 24V797000 (Power Train) was performed by the dealer. The manufacturer was not made aware of the failure. The failure mileage was unknown. | Crash: No Fire: No | Unknown |
| Apr 2025 | ENGINE | At cold start-up, engine (6.2) makes a metal-to-metal grinding sound for 60-90 seconds. After warm-up, a steady tick on the right side of the engine while running. I contacted GM and they said, " this was normal at start up". however, with me being a mechanical engineer, all of my school and working experience tells me anything grinding metal to metal is not good. | Crash: No Fire: No | Unknown |
| Apr 2025 | POWER TRAIN | P1098 coolant Control Valve malfunction and out of stock | Crash: No Fire: No | Unknown |
| Mar 2025 | ENGINE | Engine seized and now we need a new motor | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN,ENGINE | The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 30 MPH, there was an abnormal knocking sound coming from the engine compartment, after which the vehicle lost motive power. The contact was able to pull over to the side of the road. No warning lights were illuminated. The vehicle was taken to a dealer, who determined that the engine needed to be replaced. The vehicle was repaired. The contact stated that prior to the engine failure, the transmission was replaced. The manufacturer was not notified of the failure. The failure mileage was approximately 20,000. | Crash: No Fire: No Towed | 20,000 |
| Mar 2025 | POWER TRAIN | I own a 2021 GMC Sierra 1500 Duramax diesel. At around 60,000 miles, I received an engine coolant system alert through OnStar and retrieved a P1098 trouble code, which indicates a failure in the coolant control valve. This issue causes the engine fan to run excessively, creating loud noise, reduced fuel economy, and possible drivability concerns. After researching owner forums and talking to multiple service departments, I discovered this is a widespread problem among 2020–2022 GMC/Chevrolet Duramax 3.0L diesel owners. In many cases, the coolant control valve is failing prematurely, and the replacement part is on national backorder, suggesting a high failure rate. GM has not issued a recall or service bulletin to address the issue, and many customers are being told to pay out of pocket despite the systemic nature of the failure. This component is tied to engine temperature control, and failure could pose a safety risk if the engine overheats or derates unexpectedly. I am filing this complaint to document the issue and request NHTSA investigate this as a potential defect. | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact received notification of NHTSA Campaign Number: 24V797000 (Power Train); however, the dealer was unable to complete the recall and returned the vehicle to the contact in a worse condition than when the contact had dropped the vehicle off at the dealer. The contact stated that while attempting to drive the vehicle off the dealer parking lot, the check engine and reduced power warning lights flashed on the instrument cluster. The contact stated that he returned the vehicle to the dealer and was informed that the vehicle could not be repaired. The manufacturer was not made aware of the issue. The failure mileage was approximately 114,000. | Crash: No Fire: No | 114,000 |
| Mar 2025 | ELECTRICAL SYSTEM,ENGINE | My truck was part of a GM buyback program where GM Corporation bought the truck back to fix it around Aug 7th 2023 for engine problems. I am reporting this because I do not believe that GM ever reported this to NTSHA. There are also other issues happening at the same time period that should be looked into that may or may not be coincidences. At or before 10,126 miles the truck started having engine lifter and other engine issues. General Motors will not tell me exactly what was done other than lifters according to paperwork supplied. It may have had other issues like a spun bearing but it was never disclosed. Can NTSHA please look into this and information is found, could I please get the records. I asked for the paperwork of what was done while GM owned and troubleshot all the problems. I was told that information is only available to the original owner and I could not have it. It is very frustrating when General Motors Corporate use owner’s personal data as a way to hide what was done and not have to disclose required information. I am asking for service records while General Motors owned it and the service records they did to fix it. I know that there are many more engine problems that are not documented on the vehicle summary. GM will not buy back the truck over a few lifter issues. The truck was later fixed and Art Gamblin Motorsv in Enumclaw Wa, purchased it. I am told it is fixed but have no real paperwork proving this, I was able to purchase an extended warranty just in case. There is also quite a few of battery and electronic issues that do not seem normal with the car as well. The battery was replaced at 10,126 miles at the same time as the engine issues and the battery module was replaced at 29,536 miles. At 29,875 miles and 29,965 some type of communications module and On Star module was replaced. This is the around the same time as the truck was having engine issues and was eventually bought back for what is called “engine noise”. | Crash: No Fire: No | Unknown |
| Mar 2025 | ENGINE AND ENGINE COOLING,ELECTRICAL SYSTEM,ENGINE | The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 60 MPH, there was an abnormal knocking sound coming from the engine compartment, after which the vehicle lost motive power. The contact was able to pull over to the shoulder of the roadway, where the vehicle failed to restart. The check engine warning light was illuminated. The vehicle was taken to an independent mechanic, who determined that the engine had seized. The contact was also informed that the fuse box needed to be replaced. The vehicle was repaired, but the failure reoccurred. After investigating the failure, the contact related the failure to NHTSA Action Number: PE25001 (Engine, Engine and Engine Cooling). The manufacturer was not notified of the failure. The failure mileage was 63,000. | Crash: No Fire: No | 63,000 |
| Mar 2025 | POWER TRAIN | Truck started to lose power or slip on quick acceleration on highway Truck would jolt or shudder. 63000 miles. Dealer diagnosed truck needs Torque converter and a valve body replacement. No warning lights Contacted GM. Have a case number, was told to take to dealer. It’s at dealer now, getting repaired. I’m wondering if GM has a bigger problem with transmission recall | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN,ENGINE | After 2 years of owning the vehicle, after every oil change, it would indicate low oil just before an oil change causing for us to add an additional a quart of oil to keep it running smoothly. We informed the service technician of the situation on multiple occasions and no further inspection was completed, and just an oil change was serviced. After a few months we noticed the engine was running rough and a white smoke coming out of the exhaust on acceleration then the check engine light came on. We brought the car to get tires replaced and to service the check engine light, the technician stated that the check engine light a failure in the catalytic converter. We brought the vehicle to the local GMC service center, where they indicated that the we required a replacement engine because of catastrophic engine failure. We reported that the check engine light was due to catalytic converter failure. The service technician ensured that the priority was the replacement of the full engine not indicating what was the main cause of engine failure stating that the catalytic converter could have led to the failure of the engine as well. We replaced the engine, and after 3 months of vehicle being in the shop the engine was replaced. Three days after receiving the vehicle, a check engine light came on. We did not drive the vehicle until we had to return it back to the service center. The service technician stated that it is due to a lack of communication from the engine to the ECU. The technician called the following Monday stating that the check engine light was due the catalytic converter. We told the technician that was the primary reason that the customer the vehicle in the first place. We asked if there was an alternative to replacing the catalytic converter since we already paid 12k for the engine replacement. We asked if they had taken apart the catalytic converter to confirm its not a sensor issue. They replied that the codes indicates its the whole converter. | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN | See attached document for complaint. | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving approximately 75 MPH, the rear wheels locked up. The failure had occurred on several occasions. The contact stated that several unknown warning lights were illuminated. The vehicle was towed to a dealer where it was diagnosed and determined that a software update was needed. The vehicle was repaired under an NHTSA Campaign Number: 24V797000 (Power Train); however, the failure persisted. The manufacturer was not notified of the failure. The failure mileage was approximately 35,000. | Crash: No Fire: No Towed | 35,000 |
| Mar 2025 | ELECTRICAL SYSTEM | Multi functional tail gate will open on its own while driving. I have had this repaired by gm 3 times and still have issues. This problem is currently on the recall list for 2500 hd series trucks and the 1500 series trucks in Canada but not on recall in united states. This problem poses a life threatening problem while on the road due to contents of truck possible becoming projectiles to other drivers due to tailgate opening on its own . | Crash: No Fire: No | Unknown |