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 |
|---|---|---|---|---|
| Jan 2025 | ELECTRICAL SYSTEM | Assure Guard (877-831-3077) Contract number [XXX] GMC Customer Care Melissa (866-790-5600 Ext [XXX] ) Case#[XXX] Dealership: Phil Moore GMC (601-956-0150) My truck is barely 4 years old. I should not have this problem . Why is it no one guarantee the product they make? I paid too much money for this vehicle financing it as a new truck. I paid 766.95 to replace/install the shark fan antenna on the roof of my truck because it literally came loose on his own. No one (dealership, GMC, Assure Guard) would assist with repairs. The shark fin antenna started leaking water and it was wobbly where, it was no longer sealed on the body of the truck. Water leaking through out the ceiling/roof. I didn’t do anything to cause this! GMC Customer Care refused to refund nor, help with the cost of repair. I tried to file a claim with my extended warranty company(Assure Guard) contract number [XXX] - they refused to cover the antenna. I have owned several 1500 truck models, and none of them has had the antenna to fall off the vehicle. I had to return to Phil Moore, GMC a second time because they did not properly seal the antenna. This caused the whole interior of my truck to be drenched with rainwater. I am upset with the dealership, GMC and my extended warranty(Assure Guard) because I spent too much money on my vehicle to have this happen and I would like to be refunded. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Jan 2025 | SERVICE BRAKES,ENGINE,FUEL/PROPULSION SYSTEM | We have had several times where we are on highway and our truck like slams on the brakes causing us to lose control. It was a recall on it and GMC fixed it and within the same week of them fixing it it happened 3 times back to back. Making my truck to force another car to steer out of my way and actually went off the highway. Thank god it was just dirt snd he didn’t get hurt or anything. But I am scared to even drive my vehicle! It starting Happening for about a year now. And it would only do it like every couple months but now it’s has done it 6 times in the last 2 months! | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | I was notified at the dealership that my truck had metal in the oil that is causing the oil sensor pump to send a ln engine code. The fix is a new engine. | Crash: No Fire: No | Unknown |
| Jan 2025 | UNKNOWN OR OTHER | Transmission, rear wheel lock up issue. Dealer performed recall notice work. Truck still has same issue after dealer visit. When issue starts, feels like you ran over something in the road, All warning lights are on, loss of power to engine and the engine did quit working once. Door locks continue to cycle repeatedly, multiple screen warnings appear on dashboard. It appears that everything that could go wrong happens at once. Have heard transmission valve control modules is a major problem with GM 10 speed transmissions. | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | Engine knocking and metal in oil. Been to the dealership and even though it's under warranty they will not act on it due to no check engine light present. It's making it difficult to trust driving the vehicle anymore because of the thought of the engine shutting down without warning anytime. This complaint is documented and confirmed by a dealership. They made me pay the check out fee and recommended i keep driving the vehicle until the motor locks up. | Crash: No Fire: No | Unknown |
| Jan 2025 | WHEELS,ENGINE | Le Moteur Le 13 décembre 2024 le véhicule arrêté subitement je tente de le redémarrer et ne demarre plus à plusieurs reprises je branche un obd2 et cela indique crank sensor j'envoie le véhicule au dealer et me dise qu'il y a quelque chose dans la base et aujourd'hui ils y est encore Les pneus Certains Flan de pneu de ce véhicule sont fissures tous le tour des roues | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | Lifter noises, error codes for misfires, lost power | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at approximately 20 MPH, the vehicle lost motive power. The contact stated that the accelerator pedal was depressed; however, the vehicle failed to respond as needed. The contact moved the transmission lever from drive(D) to neutral(N) to reverse(R) several times and was able to drive back to the residence. The contact stated that the check engine warning light was illuminated. The contact had the vehicle towed to a local dealer. The dealer diagnosed the failure and determined that the transmission control valve had failed and needed to be replaced. The vehicle was repaired; however, the contact stated that the failure had reoccurred. The vehicle was taken back to the same dealer who advised that the transmission control valve had failed, but the parts needed to complete the repair were on back-order. The vehicle was not repaired. The contact had asked the dealer what the possibility of the same failure reoccurring after the second replacement of the control valve and the dealer advised that the valve would fail again. The vehicle was awaiting repair. The manufacturer was informed of the failure. The failure mileage was 27,676. | Crash: No Fire: No Towed | 27,676 |
| Jan 2025 | ENGINE | Multiple injector and lifter failures. Occurred on 2 separate occasions. Taken to dealer the first time. Told injector failure and lifter failure. Less than a week later experienced multiple lifter failures. Taken to dealer again for repair. They only replaced some of the affected lifters, even though TSB from GM recommends replacement of all of them. Currently awaiting failure of additional components not replaced. There was no warning of either occurrence. Was only driving 45 mph on my way home the first time. The second occasion was on initial start up at Dr office. Opened a claim with GM on my own, as dealership was negligent or unwilling to contact GMC about these failures, even though I provided them with the appropriate TSB directly from GM. | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN,ENGINE | We had to replace the transmission at 70,000 miles even though problems were reported to the dealer at 53,340. This repair costed $2300 on a 1 year old truck. Then we needed to replace a solenoid circuit which was not covered under warranty. We repaired this 2x (the second time covered). Then at 147,000 miles 9/24, there was a cylinder misfire which bent the push rod and collapsed lifter. This engine repair cost $8300.00 dollars. Who has to replace an engine on a truck that's 3 years old. This is a defect. Please help us. We have spent over $10,000 on repairs. We faithfully do our changes and service. | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | I got off work started my truck heard a few pops. As I was driving the vehicle started jerking like the brakes were being applied. Then I noticed a yellow engine light and a ESC light come on. I pulled over to check vehicle and all the lights went off. Dealer was just a few miles away. So I started back up and drove to dealer. On the way to dealer vehicle started a tapping noise. Then a new message flashed something about my steering will be affected. I got I to dealer safely. Where I left the truck for repairs. | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN | The control valve system on my 2021 gmc has malfunctioned and this is the second time, currently sitting at Nelson GM Dealer in Fergus Falls MN. I have to drive back to TN as thats where I live and the mechanic said this issue will happen again. This vehicle hasn't had recalls but I believe it was missed since this is the second time with this same issue. This is a GM wide issue as I have researched. | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | at 8500 miles the engine had lifter go out while I was driving down the highway cause to truck to vibrate and becoming on unsteady causing me to pull over in the middle of traffic. later at 36500 miles it had another lifter go out this time I was driving home at a slower speed but still cause me to have to pull over vert fast as the vehicle became unsteady and vibrated causing all the alarm to come on. Both times the truck was fixed under warranty nut they replaced it with the same parts that are causing the problems. Soon my truck will be off warranty and this will come out of my pocket. | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | Engine failed due to a loss of oil pressure. Rod bearing failed which cause metal to be dispersed throughout the engine causing the engine to seize from a sudden loss of oil pressure from oil pump failure. Engine was replaced in June 2024 failure happened in May 2024. While driving a system message came on DIC that stated pull over immediately to prevent engine damage and no oil pressure. I was driving uphill with cars on my right in the #2 lane. Engine shut off before I could pull over resulting in decreased braking power and a lack of steering. I almost hit 2 vehicles trying to pull over to get my family to safety on the right hand shoulder. I couldn’t pull over to the left hand shoulder as there was a guardrail in the way. When I got my vehicle pulled over the only thing that stopped my vehicle from going over the cliff was a bunch of wood chips on the right hand shoulder. From the time the warning lights came on to the time the engine shut off and seized was maybe 5 seconds. It took 31 days to replace the engine and the dealership did an inspection on the engine. There was absolutely no warning there was any problems until the lights came on. My wife and [XXX] and [XXX] were in the vehicle at the time this happened. It was so dangerous where we broke down California Highway Patrol stayed behind my vehicle with its lights on. It was also a fire hazard with the exhaust sitting on the dry bark. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Jan 2025 | ENGINE | I purchased this vehicle new in 2021. It is an Ultimate Denali trim level with a 6.2 engine. Within the first year, the driver's side head on the engine had a massive failure with only 7,000 miles. I started up the vehicle and was parked idling briefly when several light came on along with a rough idle and some exhaust smoke. I contacted On Star, who could not diagnose the problem. The vehicle was disabled and ended up being towed to the dealer, where it was being repaired for 10 days. The lifters, valves and push rods were replace. The mechanic admitted there was an internal GM problem with the 6.2 engine. I asked for the same repair be made on the passenger side head. The GM dealer refused, knowing of the faulty factory installed parts. The polished tailpipe tips were not replace and were stained by the black exhaust. They are still stained this day. I purchased this vehicle for my retirement to tow my RV. Now, I have been reluctant to travel because of the other head letting go on me somewhere out west, operating under a work load. I know of two other people who purchased new GM vehicles with the 6.2 engine, who experienced the same failure, with around the same mileage on their vehicles. | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN,ENGINE | L87 engine problems. I have had failed lifters, on top of transmission issues and a current oil consumption issue where I have to add two quarts of oil (sometimes more) without any indication of low oil. I took my vehicle into the local dealership and the technician asked if I had gotten any low oil indicator and I stated no. He proceeded to tell me it had little to no oil in it. Imagine this at highway speeds and sudden engine seizure. | Crash: No Fire: No | Unknown |
| Jan 2025 | POWER TRAIN | Transmission has a hard shift when coming out of each gear. 2nd to 1st shifts hard and jolts entire vehicle a head. Feels like a slip or difficulty in shift. | Crash: No Fire: No | Unknown |
| Dec 2024 | ELECTRICAL SYSTEM | my truck keeps having this same issue since [XXX], always take it to team Gillman second august 26 same reason they replaced the battery but is a manufacturing defect while i am driving stops out of sudden AND THIS IS THE THIRD TIME THEY SUPPOSED TO CALL ME I HAVENT RECEIVE NO CALL IS AT TEAM GILLMAN SAME REASON ONLY HAS 18000 MILES MY NAME IS [XXX] CELL [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Dec 2024 | ELECTRICAL SYSTEM,LATCHES/LOCKS/LINKAGES | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at various speeds, the tailgate opened unintendedly. No warning light was illuminated. The vehicle was taken to the dealer but was not diagnosed or repaired. The dealer informed the contact that the VIN was not included in GM Campaign Number: N232426401. The manufacturer was not notified of the failure. The failure mileage was approximately 57,000. | Crash: No Fire: No | 57,000 |
| Dec 2024 | POWER TRAIN,SERVICE BRAKES,ENGINE | I received a notice of a recall for a known problem with GMC transmissions. it is very well known that these transmissions lock up and cause problems with braking and can cause the vehicle to slide off the road when the tires lock up. it also causes hard shifting, which I have experienced. GMC said they will not fix the transmission, they instead will add a device to monitor the transmission, so when the transmission locks up and causes an accident, it will let me know that it was the transmissions fault!!! How is this legal? they will let me know that their transmission caused the accident after the fact? why not fix it? typical of government to do nothing about safety... and instead make laws that allow big corporations and government to make money off of peoples deaths! | Crash: No Fire: No | Unknown |
| Dec 2024 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving at various speeds and downshifting, the rear wheels locked up with the parking brake warning light flashed on the instrument panel. The vehicle would resume normal operation soon after the failure. The vehicle was taken to a dealer where the contact was informed that there was a pending NHTSA Campaign Number: 24V797000 (Power Train) on the vehicle for the failure. The contact was informed that there was a temporary fix on the vehicle to repair the defect. After the temporary fix was performed, the contact experienced the failure twice within a week. The contact received a call that the permanent fix was available; however, soon after the repair was performed, the failure immediately occurred upon leaving the dealer. The manufacturer was notified of the failure, and the contact was informed that he would receive a callback. The vehicle was not repaired. The failure mileage was approximately 75,000. | Crash: No Fire: No | 75,000 |
| Dec 2024 | LATCHES/LOCKS/LINKAGES | The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 40 MPH, the message that the tailgate was opened was displayed, and the contact became aware that the tailgate had opened. The contact pulled over to the right side of the road to close the tailgate. The vehicle was not taken to an independent mechanic or dealer to be diagnosed or repaired. The contact stated that the VIN was not included in NHTSA Campaign Number: 24V060000 (LATCHES/LOCKS/LINKAGES). The manufacturer was notified of the failure and opened a case and referred the contact to the NHTSA Hotline to report the failure. The failure mileage was 41,000. | Crash: No Fire: No | 41,000 |
| Dec 2024 | POWER TRAIN | The contact owns a 2021 GMC Sierra 1500. The contact received notification of NHTSA Campaign Number: 24V797000 (POWER TRAIN); however, the part to do the recall repair was unavailable. The local dealer was contacted, and it was confirmed that the part was not yet available. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The contact stated that the transmission was shifting hard while driving. The local dealer was notified of the failure. The cause of the failure was not yet determined. The manufacturer was not made aware of the issue. The failure mileage was 120,000. VIN tool confirms parts not available. | Crash: No Fire: No | 120,000 |
| Dec 2024 | POWER TRAIN | transmission has a shudder when accelerating and after shifting through all gears (8speed) during cruise mode when going on an incline as in overpass it starts to shudder and seems like it is trying to find the right gear to go into . | Crash: No Fire: No | Unknown |
| Dec 2024 | ENGINE | The engine blew up at 67,000 mile while driving down the road. Not sure what happened but there was no warning signs at all. The dealership said they couldn’t know for sure what happened but most likely the oil pump went bad. I have spoken with a few people that have had this same problem with the 6.2 liter engine. It needs to be looked into because this could have caused a major accident on the highway. | Crash: No Fire: No | Unknown |