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 |
|---|---|---|---|---|
| Jun 2026 | ENGINE | Catastrophic engine failure the connecting rod went through the block. It is my understanding that Defective Components: Manufacturing defects in the connecting rods and crankshafts can reduce oil film strength, leading to severe wear, metal debris, and catastrophic engine could be the proiblem | Crash: No Fire: No | Unknown |
| Jun 2026 | STEERING,POWER TRAIN,ELECTRICAL SYSTEM | power steering locked up while driving. multiple dash lights turned on, on its own after the issue, 4wd, emergency brake, abs, and other ones im not sure what they are. took it to the dealership for a recall and told them the issue that happened. | Crash: No Fire: No | Unknown |
| Jun 2026 | STEERING,POWER TRAIN,ELECTRICAL SYSTEM | power steering locked up while driving. has been inspected and repaired by manufacturer. recall. | Crash: No Fire: No | Unknown |
| May 2026 | POWER TRAIN,ENGINE,FORWARD COLLISION AVOIDANCE | The truck randomly will not detect that it was shifted into park. Shifting between gears and back to park does not automatically fix the the issue and has taken up to 10 mins to turn the truck off. The adaptive cruise controls stopped working and can still use regular cruise control. Just not adaptive. It appears greyed out. The truck has thrown the error code: P1098, Engine Coolant Control Valve Position Sensor Minimum Stop Performance. The truck would go into limp mode until the error was cleared. This error has appeared 4 times over the past five months. The most recent date of it happening was today. 06/30/2026 | Crash: No Fire: No | Unknown |
| May 2026 | POWER TRAIN | The truck has a studder that comes from the transmission when at highway speeds. the studder can be felt at random intervals (seconds) from all passengers. The studder is also present on starting up a slope or accelerating from a stop at a slow pace. when accelerating slowly the jerk is more prominent. We have taken it to the GM Dealership, they confirmed the issue was present. The dealership said the GM guidence was to 1st try a re-program and then replace the torque converter. The program flash was unsuccessful, then we paid $4000 to change the torque converter. The Tech stated that this was the GM suggested fix, but noted that we are changing the fluid also which could mask the issue if it is the valve body causing an issue. The replacement torque converter and fluid did somewhat reduce the issue for a short period of about 2 months before it has returned as it did before. The next option from the dealership is in excess of $8,000 for a remanufactured transmission which is outside our reasonable spend, when we dont expect the remanufactured transmission will have any better valve body components. The recent recall did not cover my gas 6.2L sierra 1500, although it clearly is insufficient stating that it just a warning that there is a safety risk present. The valve body of the transmission appears to be an issue across all models and the recall addresses that it is present. We continue to drive this as the primary family vehicle with the hesitation and jerking present as GM dealer offered no support other than $8,000 remanufactured transmission on top of the $4000 we already spent. I believe the recall was insufficent in covering the Gas models with the exact same transmission and known issue. I also believe the offered solution continues to put those driving at risk. | Crash: No Fire: No | Unknown |
| May 2026 | STEERING,ELECTRICAL SYSTEM,FUEL/PROPULSION SYSTEM | My truck will not start when I press the push-button ignition. After waiting a few seconds and trying multiple times, it typically starts on the third attempt. Additionally, it will not restart after the auto stop feature activates at stop signs or traffic lights. This is very concerning, especially when pulling into oncoming traffic, as I’m worried the truck could shut off while I’m crossing. I have already had the battery, starter, and alternator checked, and all components tested fine. However, the issue is still occurring. There are also no warning lights or messages displayed on the dashboard. | Crash: No Fire: No | Unknown |
| May 2026 | ENGINE | While driving at normal highway speeds, I got a warning light for engine overheat condition and cooling fans came on. I also got a warning that the engine would go to reduced power. I reported this issue to my local GMC dealer. Was told that this was a comm problem with this engine however: my vin number indicated that this vehicle was not covered under warranty N252508341. I was advised to bring it in for a $250 diagnostic check and repairs could not be made for at least 2 months because of backlog. Took my truck to a local vehicle repair shop where they diagnosed a faulty coolant control valve and replaced it for me for $2388.43. Why did GMC desert me? | Crash: No Fire: No | Unknown |
| May 2026 | STEERING,ELECTRICAL SYSTEM | Shift to park dings continuously and vehicle won’t turn off draining battery leaving doors unlocked. Don’t want to force into park and break anything more. | Crash: No Fire: No | Unknown |
| May 2026 | ELECTRICAL SYSTEM,ENGINE,FORWARD COLLISION AVOIDANCE | 2021 GMC Sierra AT4, VIN [XXX] , NHTSA Campaign 25V-274, GM Case XXX. Brake pad monitor failed at 128,923 miles -- 24 miles after leaving Penske Chevrolet (released at 128,899, RO XXX, 04/17/2026). Brakes became spongy immediately following service. Monitor disabled entirely to stop recurring red Service System alert. Root cause is a burnt fuse block ground fault confirmed in writing by two GM-authorized dealers. Ray Skillman (RO XXX, 06/05/2025) documented the fault then deleted Labor Operation 14BUZ ENGINE ELECTRICAL from the recall repair work order. Penske documented verbatim: "all of these other faults share this same ground circuit." The recall repair at Ray Skillman used a remanufactured short block instead of a complete engine per N252494002. The original seized-engine oil pan has never been replaced across three dealerships and 128,000 miles. GM's own Part 573 filing states this defect "increases the risk of a crash." I drove 300 miles on an interstate on 04/22/2026 with active brake warning and no loaner because GM Executive Resolution refused to authorize one. Three GM dealers have inspected this vehicle. GM Executive Resolution Team [XXX] ) has not returned calls or emails and has not confirmed in writing this vehicle is safe to operate. OnStar issued a Critical Alert for P0617 on 04/15/2026. Zero brake faults existed in the 13 months prior to the Penske visit. This is a direct continuation of unresolved electrical damage from a botched federal safety recall repair at 384 days and counting. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| May 2026 | ELECTRICAL SYSTEM,ENGINE,FUEL/PROPULSION SYSTEM | Coolant Control Valve | Crash: No Fire: No | Unknown |
| May 2026 | POWER TRAIN,ENGINE | Right after i bought the car I had a very bad misfire on cylinder 1, the car would shake at idle. Took to dealership and they said they replaced all the spark plugs and replaced cylinder 1 coil. about a week later the misfire and shaking started again but this time it would come and go. the check engine light would be on then it would go away for a bit and then come back on over and over again. The only thing that seemed to work is if i disabled the stop and go start system and put the car in L9 to disable the AFM. This seems to work and I have since bought a disabler for these systems. However, there is still a vibration at idle and i feel that its a temporary fix to a bigger issue. This is my daily driver and constantly have my children in the car and just want the car to be safe for everyone. The transmission downshifts rough and at times seems to slip/lock up while driving. I haven't brought it to the dealership for this as of yet. | Crash: No Fire: No | Unknown |
| May 2026 | ENGINE | Engine has a terrible shake, and I was informed by a mechanic that it has a misfire and no compression in piston number seven | Crash: No Fire: No | Unknown |
| May 2026 | ENGINE | I have the same model and year for GMC as bulletin 25NA-185, Engine Coolant Control Valve Failures on 3.0L Duramax (Dec 4, 2025), and am experiencing the same exact issue. Apparently my VIN is not included and I can't get an answer from GMC or the local dealer why it's not covered or how to have it reviewed to be added. | Crash: No Fire: No | Unknown |
| May 2026 | ENGINE | Coolant control valve not working correctly exhaust fan on high all the time but is never overheating this has been going on for a week it shows there is a 150000 mile warranty on it but not for mine | Crash: No Fire: No | Unknown |
| May 2026 | POWER TRAIN | Coolant control valve has failed and caused the check engine light to occur is available for inspection. Could cause the car to overheat and cause harm to myself or others Yes has been confirmed by dealer No GM has a special coverage out for the specific vehicle and model years for this vehicle, but are stating that my vehicle does not pertain to that coverage. | Crash: No Fire: No | Unknown |
| May 2026 | STRUCTURE | The contact owns a 2021 GMC Sierra LD Crew. The contact stated that while driving on the highway at an undisclosed speed, the vehicle's bedrail attachment fully detached from the vehicle. The vehicle was not diagnosed or repaired. The manufacturer was not notified of the failure. The failure mileage was unavailable. | Crash: No Fire: No | Unknown |
| May 2026 | ENGINE | Engine coolant control valve needed to be replaced. Special coverage (N252508341) was issued out by GM to fix this problem on 2021 GMC Sierra 1500 vehicles. | Crash: No Fire: No | Unknown |
| Apr 2026 | ENGINE | Driving normal traffic . Started hearing ticking . Check engine light flashing ,service esc and braking system light up. Parking not loud ticking from engine bay | Crash: No Fire: No | Unknown |
| Apr 2026 | STEERING,ELECTRICAL SYSTEM | Driving down road and had total loss of power steering and yes it is available for inspection. Almost drove it off the road due to loss of steering Yes, it happened to be a failed main grounding strap that created the issue. The dealership made the repair. No, it was inspected and repaired by the dealership Yes, started with loss of power steering, then truck died and these codes popped up: Low fuel code, but tank was full; trailer brake system code; side detection code and esc traction control code. | Crash: No Fire: No | Unknown |
| Apr 2026 | SUSPENSION,SERVICE BRAKES, HYDRAULIC | The contact owns a 2021 GMC Sierra 1500. The contact stated that while her son was driving 55 MPH and depressing the brake pedal, the vehicle failed to slow down as intended. The driver attempted to use the parking brake to slow the vehicle, but the vehicle failed to slow down. The message “Braking System Failure” was displayed. The driver pulled over to the side of the road, and the passenger’s side front wheel detached and started leaning to the right before the vehicle came to a stop. The driver exited to inspect the vehicle and became aware that the front passenger’s side wheel was lying on the ground. The vehicle was towed to an independent mechanic, but was not diagnosed. The vehicle was then towed to another dealer, where it was diagnosed, and it was determined that the passenger’s side upper and lower control arms, ball joints, rack and pinion, brake rotor and pads, hub, outer tie rod, brake line, speed wheel sensor, wheel and tire, and suspension parts needed to be replaced. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 77,000. | Crash: No Fire: No Towed | 77,000 |
| Apr 2026 | UNKNOWN OR OTHER,ENGINE | Driving and lost all power to truck annd lost control. Was able to coast truck with no accidents. all lights turned on dash board. Engine stating to make horrible noise. Cylinder 1 had a collapsed lifter which cause the failure. They replaced all lifters on the left side. They stated that batch of lifters were faulty. Requested to have the lifters on the right side replaced since they are the same batch but they refused. They would fix once or if they collapse but since they working they would not change them. Called GMC, reported it to them. The three people I spoke with had no idea about lifter problems and it was the first they had heard of it. Multiple complaints have been reported by customers. They did not want to give permission to replace the right side or extend the warranty. When the right side give out, if I am going at high speeds on the freeway, an accident could occur causing injury or death. I know they have a recall on prior GMC but my truck is not included. | Crash: No Fire: No | Unknown |
| Apr 2026 | UNKNOWN OR OTHER | Engine coolant control valve | Crash: No Fire: No | Unknown |
| Apr 2026 | UNKNOWN OR OTHER,ENGINE | Coolant control valve failing. Warranty not covering this part. Seems to be a manufactured issue. Happening on a lot of 2021 GMNC Sierras with the 3.0l Duramax. | Crash: No Fire: No | Unknown |
| Apr 2026 | ENGINE | My L87 engine has failed due to a manufacturing issue. The recall number for this issue is N252494000. Upon contacting GMC, they state that my VIN number is not included in this recall despite having the same exact issues. I took the vehicle into a mechanic as soon as a problem had arose. | Crash: No Fire: No | Unknown |
| Apr 2026 | POWER TRAIN,ENGINE,FUEL/PROPULSION SYSTEM | While driving into work, I noticed a knocking sound from the outside of the vehicle. Once parked, upon further inspection I narrowed down the area of the noise to the bottom rear of the engine/front of transmission. Fortunately, I was able to park in front of my office building and wasn’t stranded on the side of the road but under different circumstances it could've been the side of a busy highway or hours from home. I had the vehicle towed to the dealership I originally purchased from, the dealership was able to duplicate the issue with me present. Later that afternoon I was informed that the engine had failed and a replacement would be ordered. There was no prior indication of a problem or warning/CEL’s. The engine failed after the dealership had completed the engine recall ( pico test and 0-40W oil change ) related to the vehicle. I am reporting this in hopes that it helps with the investigation. This has been very disappointing for me as I have supported the brand of vehicle for many years. Only to have many issues under 80,000 miles and to lose confidence in the vehicle I purchased and the company. | Crash: No Fire: No | Unknown |