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 |
|---|---|---|---|---|
| Mar 2025 | AIR BAGS | Airbag system did not deploy but smoke in cabin during a crash. Video of front, rear and inside cabin shows the rear end passenger side impact at an estimated 45-50 MPH. I saw smoke in cabin, disturbed with anxiety after crash waiting for bags to deploy accidentally. The airbag deployed red light illuminated notifying an airbag deployment. I received a GM message through the vehicle report application stating that my airbag system malfunctioned and I needed to take the vehicle to a service department for repair as soon as possible. This crash was a total loss of the GMC Sierra, this was how hard the vehicle was hit. Why did the airbag system smoke? Why did the airbags not deploy? Why did I receive a Malfunctioning Airbag system message from GMC? Video shows that if the airbag system would have deployed on the steering wheel I would have had less head and neck trauma when whipping backward and then forward. | Crash: Yes Fire: No Injuries: 1 Towed Medical attention | Unknown |
| Mar 2025 | ENGINE | I was driving 50mph when my check engine light started flashing. The engine had very little power and there was a new consistent engine knock. I took to GMC dealership and they informed me that half of the engine lifters failed and a pushrod was bent. There was no warning prior to the incident. I have had the vehicle serviced only at the dealership and have only used premium fuel. The truck has 88,000 miles. | Crash: No Fire: No | Unknown |
| Mar 2025 | POWER TRAIN,ELECTRICAL SYSTEM,ENGINE | [XXX], I PURCHASED A 2021 GMC SIERRA 1500 FROM FAULKNER CHEVROLET IN BETHLEHEM, PA. I TEST DROVE THE VEHICLE BEFORE PURCHASE AND IT SHOWED NO INDICATION OF ANY MECHANICAL ISSUES THAT I WAS ABLE TO DETECT. I WAS SHOWN BY THE DEALERSHIP THE CARFAX AND WAS INFORMED THAT THERE ARE CURRENTLY NO RECALLS FOR THE VEHICLE. I WAS LED TO BELIEVE THAT THE VEHICLE WAS IN GOOD CONDITION AND SAFE TO DRIVE AND, THEREFORE, AGREED TO PURCHASE THE VEHICLE FOR THE AFOREMENTIONED PRICE (INCLUDING TAX AND TITLE FEES). I PURCHASED THE VEHICLE WITH 60,077 MILES ON IT, AND AFTER DRIVING IT NORMALLY FOR ONLY 5 DAYS (ON [XXX]) IT BROKE DOWN AND I WAS STRANDED ON THE HIGHWAY 16 HOURS FROM HOME. I WAS ABLE TO GET THE VEHICLE TOWED AND PAID $1,200 FOR THE STARTER TO BE REPLACED, WHICH IS WHAT THE MECHANIC SUGGESTED BUT THIS ENDED UP BEING ENTIRELY UNNECESSARY AS THE REAL ISSUE WAS DUE TO A CATASTROPHIC DEFECT IN THE ENGINE. AFTER THE STARTER WAS REPLACED, I WAS DRIVING THE VEHICLE ONLY A FEW DAYS LATER (ON [XXX]) AND IT SUFFERED A CATASTROPHIC ENGINE FAILURE WHILE DRIVING 70MPH ON THE HIGHWAY. I LOST CONTROL OF THE VEHICLE AND NEARLY GOT IN A COLLISION WITH ANOTHER VEHICLE. I WAS ABLE TO GET THE VEHICLE TO THE NEAREST AUTO SHOP AND AFTER INSPECTING THE VEHICLE THEY INFORMED ME THAT THERE IS A SERIOUS ENGINE ISSUE RELATING TO A SEIZED BEARING AND THE ENGINE WILL NEED TO BE REBUILT ENTIRELY. AT THIS POINT IT HAD BEEN ONLY 12 DAYS SINCE THE PURCHASE AND THE ODEMETER READ 61,662 (1,585 MILES DRIVEN SINCE PURCHASE). DUE TO THE FAULTY VEHICLE, I WAS FORCED TO PAY TO HAVE THE VEHICLE SHIPPED FROM THE LOCATION WHERE IT BROKE DOWN TO THE DEALERSHIP WHERE I ORIGINALLY BOUGHT IT (AROUND $1,200). FAULKNER CHEVROLET KNOWINGLY SOLD ME AN UNSAFE VEHICLE THAT THEY WERE WELL AWARE HAD A DEFECTIVE 6.2L V8 ENGINE. THIS DEFECT IS CURRENTLY UNDER INVESTIGATION BY THE NHTSA AND FAULKNER CHEVROLET PURPOSEFULLY OMMITTED THIS CRUCIAL INFORMATION UNTIL AFTER THE VEHICLE WAS SOLD. CLEARLY, THIS IS AN UNETHICAL BUS INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Mar 2025 | ENGINE | I've now had 2 engines fail catastrophically, One at 19,191 miles and the second failure at 80,661. Both are the 6.2L engine. The first had crank bearings that were black. The second I was not informed of the cause but that it was seized leaving me stranded on the roadside. | Crash: No Fire: No | Unknown |
| Mar 2025 | ENGINE | Engine failed and had to be replaced. GMC was absolutely no help had to bring to local gas station where i had to pay almost $12,000 to get it fixed. The truck has been in shop frequently for oil issues with this motor but GMC just jerks you around. I am in sales and need my vehicle to support my family | Crash: No Fire: No | Unknown |
| Mar 2025 | ENGINE | While driving the vehicle shut off in the middle of the roadway. It sat in the road till it got towed. Brought it to the dealership where it was purchased and they said the engine was blown. Themis vehicle is equipped with the 6.2 motor. It happened February 16th. The dealership confirmed the engine failed. It is siting currently at the dealership and could be available for inspection. | Crash: No Fire: No | Unknown |
| Feb 2025 | POWER TRAIN,ENGINE | Subject: Complaint Regarding Recurring Engine Failure in 2021 GMC Sierra AT4 Dear National Highway Traffic Safety Administration, I am writing to formally express my concern regarding recurring engine failures in my 2021 GMC Sierra AT4 (6.2L engine). At 23,000 miles, the vehicle suffered a complete breakdown due to failure of cylinder #8, lifters, and push rods. General Motors covered the repairs at that time. However, at 97,000 miles, the exact same issue reoccurred, resulting in significant engine damage. The dealership diagnosed a misfire in cylinder #8, leading to the removal of the right cylinder head, where they found a bent push rod, spun lifter, damaged camshaft lobe, and lifter roller. The repair estimate totals $9,746, but GM has refused to cover the costs, despite us having an extended warranty purchased from the dealership. This recurring failure raises serious concerns about engine reliability and manufacturing defects in General Motors vehicles. I urge the NHTSA to investigate this issue, as multiple GMC and Chevrolet owners have reported similar problems with the 6.2L engine lifter and camshaft system. This is not just a costly repair but a potential safety hazard that GM has failed to properly address. Thank you for your attention to this matter. I appreciate any guidance or action the NHTSA can take to hold GM accountable and ensure consumer protection. | Crash: No Fire: No | Unknown |
| Feb 2025 | LATCHES/LOCKS/LINKAGES | The contact owns a 2021 GMC Sierra 1500. The contact stated that the tailgate opened unintendedly while driving, and while the vehicle was parked. The contact stated that the failure had been recurring. The vehicle was taken to the dealer but was not diagnosed or repaired. The contact related the failure to GM Campaign Number: N232426400. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline to report the failure. The failure mileage was approximately 76,000. | Crash: No Fire: No | 76,000 |
| Feb 2025 | ENGINE | AFM lifters failed which caused cam shaft to collapse under 35k miles. Had to remove while front end to repair | Crash: No Fire: No | Unknown |
| Feb 2025 | ENGINE | My Vehicle went into the dealer on January 21, 2025. My initial complaint was tapping noise, I was advised that my vehicle had collapse lifters issue several days later I was informed that they have found metal shards in the lower end and found a bad crank bearing and crank. I was told that the vehicle will need an engine replacement, and that the engine is on back order with no date of fulfilment. My vehicle has 66,700 miles I was advised was out of warranty and that GM will only cover half of the estimated cost of 11,000.00. | Crash: No Fire: No | Unknown |
| Feb 2025 | VISIBILITY/WIPER | Wipers work intermittently | Crash: No Fire: No | Unknown |
| Feb 2025 | ENGINE | The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at approximately 80 MPH, the vehicle stalled and failed to return to normal operation. No warning light was illuminated. The vehicle was towed to be diagnosed. The contact was informed that the rod bearings needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 134,000. | Crash: No Fire: No Towed | 134,000 |
| Feb 2025 | ELECTRICAL SYSTEM | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, the transmission slammed into gear and the rear wheels locked up. In addition, the vehicle decelerated independently. The vehicle was driven to the shoulder of the road and turned off. The vehicle was restarted, and the contact noticed that the vehicle was independently reset. The vehicle was taken to the dealer where it was diagnosed with a failed wiring harness. The contact was informed that the wiring harness needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and a case was filed. The contact was advised to contact the NHTSA Hotline and report the failure. The failure mileage was approximately 60,129. | Crash: No Fire: No | 60,129 |
| Feb 2025 | POWER TRAIN,ENGINE | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 55 MPH, the vehicle started making a knocking sound. There were no warning lights illuminated. The contact picked up his son from school and drove the vehicle to the dealer. The contact stated that while depressing the accelerator pedal, the knocking sound became louder, and the vehicle was losing motive power. The vehicle was taken to a dealer and diagnosed with engine failure. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 58,522. | Crash: No Fire: No | 58,522 |
| Feb 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at various speeds up an incline, the vehicle was vibrating and shuddering. The failure persisted over time. There were no warning lights illuminated. The vehicle was taken to the local dealer, but the vehicle was not diagnosed or repaired. The vehicle was taken to a transmission shop, and it was determined that the transmission needed to be replaced. The manufacturer was not contacted. The approximate failure mileage was 68,000. | Crash: No Fire: No | 68,000 |
| Feb 2025 | ENGINE | While driving on the highway the engine 6.2 GM seized suddenly at high speed. The truck shut off completely and left rolling without any control. I had work my way accross lanes to the breakdown lane. While doing so I was almost hit by an 18 wheel trailer truck, who luckily was able to change lanes to avoid hitting me. The reason I was almost hit was because of my low speed since I had now power or acceleration. | Crash: No Fire: No | Unknown |
| Feb 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at various speeds and depressing the accelerator pedal, the vehicle hesitated to respond and shuddered. The vehicle was taken to the dealer, where the fuel tank was cleaned, and the contact added fuel treatment to the fuel, as recommended by the dealer; however, the failure recurred. The contact stated that while driving from a complete stop, uphill, and while driving 50 MPH, the vehicle shuddered and experienced erratic transmission shifting. The check engine warning light was illuminated. The vehicle was taken to Dixie Buick GMC (14565 S Tamiami Trl, Fort Myers, FL 33912); where it was determined that the vehicle was experiencing a abnormal shudder. The dealer replaced the transmission fluid; however, the failure persisted. The contact stated that the failure had become progressively worse and mostly occurred at 1,200 RPM. The dealer was contacted, and an appointment was scheduled for diagnostic testing. The vehicle was not diagnosed or repaired. The contact related the failure to NHTSA Campaign Number: 24V797000 (Power Train); however, the VIN was not included. The manufacturer was notified of the failure. The failure mileage was approximately 8,000. | Crash: No Fire: No | 8,000 |
| Feb 2025 | ENGINE | I purchased a new 2021 GMC Sierra Denali with a 6.2L engine on 03/05/2022. On November 10, 2022, I started the truck, and the engine seized up. The truck had 9018 miles on it and 274 engine hours. The main bearings and possibly the connecting rods bearings was the problem. On January 27, 2023, I finally got a new engine installed in my truck. I had to pay for the repairs. | Crash: No Fire: No | Unknown |
| Feb 2025 | ENGINE | Driver side lifters collapsed and push rods failed on freeway without warning at 12900 miles on truck. | Crash: No Fire: No | Unknown |
| Feb 2025 | SUSPENSION,ENGINE AND ENGINE COOLING | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, there was an abnormal clunking sound coming from the rear suspension. The check engine warning light was illuminated. The vehicle was taken to the dealer, who diagnosed a failure with the rear suspension. The vehicle was repaired, but the failure reoccurred 4,000 miles later. The contact stated that while reversing, the contact heard an abnormal clunking sound coming from the rear suspension. The contact also stated that there was also a strong antifreeze odor permeating the interior of the vehicle. The vehicle was taken back to the dealer, but not yet diagnosed. The vehicle was not repaired. The manufacturer was notified of the failure, and a case was opened. The failure mileage was 38,000. | Crash: No Fire: No | 38,000 |
| Feb 2025 | POWER TRAIN,VEHICLE SPEED CONTROL,ENGINE | On the morning of 1/19/25, my 2021 GMC Sierra 6.2L AT4 went into limp mode heading south on HWY 207 in Leavenworth, WA at approximately 60 m.p.h. Fortunately, I was able to avoid a rear end collision. I quickly turned the truck off in the middle of the road and restarted it with a CEL. When I returned home almost 180 miles away, my local mechanic diagnosed a code P0303 and cleared it. Since, the truck has continued to shutter at various speeds without throwing a code. It is currently at Haselwood GMC in Bremerton, WA being scanned, recorded, and findings set to GM waiting for resolve. I have notes, exact dates, times, call records, return voice mail messages, and dealership personnel spoken to, etc. The dealer’s lead technician and I were able to replicate the shutter on a road test together on 1/27/25 at 3 p.m. after having driven just 10 miles. During my visit on the morning of 1/30/25, the lead technician stated he has since been able to replicate the shutter seemingly getting worse. I was strongly encouraged by the service manager, service writer, and lead technician their collective “personal recommendation” was to not take the truck back. Haselwood has had the truck since 1/27/25. Still awaiting a response and resolution. | Crash: No Fire: No | Unknown |
| Feb 2025 | ENGINE | lifters in the left and right side snapped into 3 pieces. Caused engine failure happened 2 different times. All before 50,000 miles. The first time was before 30,000 miles. | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | Engine failure | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact received notification of NHTSA Campaign Number: 24V797000 (Power Train); however, the contact believed that the remedy offered would cripple the vehicle and interfere with his work. The contact works in Alaska and the remedy involved the transmission being limited to fifth gear, preventing the possibility of a wheel lock up condition, which could occur while downshifting from eighth gear. The manufacturer was made aware of the issue and advised the contact to find a dealer that could repair the transmission. The contact had not experienced a failure. Parts distribution disconnect. | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN | The engine locked up with no warning I called the dealership and they said it was out of warranty as it has 77000 miles. upon further investigation I found that the front main bearing on the engine had gone bad and caused the engine to lock up. GMC refused to accept any responsibility for the failure. | Crash: No Fire: No | Unknown |