Complaint volume
424 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
2020 GMC Sierra Complaints
424 consumer-submitted complaints on record for the 2020 GMC Sierra, grouped by component category.
424 Total complaints
11 Crash reports
4 Fire reports
6 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, electrical system. Use those categories as a test-drive checklist instead of judging the vehicle from the total count alone.
Severity flags
Enriched records include 11 crash reports, 4 fire reports, 6 injury reports, and 0 fatality reports. These fields come from complaint records and should be read in context.
Mileage clue
Mileage is available on 118 complaints, with an average reported failure mileage of 44,233 miles. Compare that with the mileage on the listing.
Questions to ask the seller
- Have you had any problems related to engine, power train, electrical system?
- 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 2020 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.
2020 GMC Sierra
Build buyer checklist Compare with other years Sends year, make, and model to pre-fill your checklist.
How severe are the 2020 GMC Sierra complaints?
11 Crash
4 Fire
6 Injury
0 Fatality
28 Towed
4 Medical attention
What are the most common 2020 GMC Sierra complaint categories?
ENGINE 125
POWER TRAIN 36
ELECTRICAL SYSTEM 21
POWER TRAIN,ENGINE 17
SERVICE BRAKES 16
STEERING 14
UNKNOWN OR OTHER 14
ENGINE AND ENGINE COOLING 9
SUSPENSION 9
ELECTRICAL SYSTEM,ENGINE 8
424 total complaints on record
Latest complaints
| Date | Component | Summary | Severity | Mileage |
|---|---|---|---|---|
| Mar 2026 | VEHICLE SPEED CONTROL,ENGINE AND ENGINE COOLING | The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at 65 MPH, the DEF tank failed. The vehicle went into three phases of LIMP Mode and the vehicle unexpectedly decelerated while driving. The DEF system service message was displayed. The vehicle was taken to the local dealer, where it was diagnosed with DEF tank failure, and the tank needed to be replaced, even though the tank was full. The part was on backorder for several weeks. The contact was not provided with a loaner. The vehicle was repaired. The manufacturer was contacted and opened a case, but no additional assistance was provided. The failure mileage was approximately 70,000. | Crash: No Fire: No | 70,000 |
| Mar 2026 | ENGINE AND ENGINE COOLING,ENGINE | The contact owns a 2020 GMC Sierra 1500. The contact stated that the vehicle made an abnormal sound while idling. There was no warning light illuminated. The vehicle was taken to the dealer, where the engine was disassembled, and the dealer determined that the crankshaft and the thrust bearings had failed. The vehicle was repaired. The contact related the failure to NHTSA Action Number: EA25007 (Engine, Engine and Engine Cooling). The manufacturer was notified of the failure and partially covered the repair cost. The failure mileage was 60,000. | Crash: No Fire: No | 60,000 |
| Mar 2026 | ENGINE | To the best of my knowledge… My 2020 GMC Sierra Denali with a 6.2L engine and 74,000 miles had a complete engine replacement. One lifter on bank 2 was stuck, and the push rod in the cylinder was bent. The engine made a popping noise when starting. I took it to a GM dealership, where they quoted $9,200 to repair the issue or $9,600 for a brand-new engine with a 3-year/100,000-mile warranty. I know there is open recalls for 21’-24’ Models, but I would like some help with mine. This kind of problem shouldn’t happen on a GMC - loaded truck with only 74,000 miles. Thank you! | Crash: No Fire: No | Unknown |
| Mar 2026 | POWER TRAIN,ELECTRICAL SYSTEM | Truck broke down with a rear-wheel lockup and had the transmission replaced in June 2025. In December 2025 and February 2026, truck lost power two times and entered limp mode while on a major highway and major interstate. The problem was misdiagnosed in June 2025, diagnosed properly in December 2025, but not properly repaired, and diagnosed properly in February 2026. All three times the vehicle had this issue, two of the same exact DTCs were present. This is a safety defect, and I have lost all confidence that the vehicle is reliable enough and safe enough for myself and my family. | Crash: No Fire: No | Unknown |
| Mar 2026 | ENGINE | The 10L80 transmission had a catastrophic failure just outside of the GM warranty. At under 70K miles the pump gears came apart and sent metallic debris throughout the entire transmission and exhaust gaskets converter next to the transmission. These will need to be replaced. I have found multiple cases online with this 10L80 transmission where there has been significant problems with these transmissions blowing up or even causing momentary lockup with the wheels. This transmission is notorious for problems but has not yet been recalled. My mom and nephews were in the vehicle when it broke down putting their safety at risk on the the highway. This problem was confirmed by the GMC dealership here in Ruston, LA. The dealership has done the mechanical inspection. The engine started making an extremely loud noise and the warning lights did not even come on until I attempted to start it later after the breakdown. | Crash: No Fire: No | Unknown |
| Mar 2026 | ENGINE AND ENGINE COOLING | The contact owns a 2020 GMC Sierra 1500. The contact stated that while starting the vehicle, the engine hesitated while turning over. The vehicle started with the check engine warning light illuminated, and the DEF (Diesel Exhaust Fluid) sensor light was illuminated. The message “94 miles before vehicle enters LIMP Mode" was displayed and instructed the contact to see the Diesel Exhaust Fluid section of the Owner's Manual. The vehicle was restricted to a 65 MPH max speed. The vehicle was towed to a dealer, where it was diagnosed, and it was determined that the DEF tank pump assembly had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was 121,000. | Crash: No Fire: No Towed | 121,000 |
| Mar 2026 | ENGINE | Vehicle has 28,000 miles and auto shop states that the engine is blow, it's knocking and vibrating throughout the engine. | Crash: No Fire: No | Unknown |
| Mar 2026 | ELECTRICAL SYSTEM | Odometer Fraud. The contact attempted to purchase a 2020 GMC Sierra 1500. The contact discovered a mileage discrepancy. The vehicle was a private sale. At the time of purchase, the mileage was 75,000. At the time of registration, the Carfax Report indicated that the mileage was 175,000. | Crash: No Fire: No | 175,000 |
| Mar 2026 | ENGINE | Engine failure at 84000 | Crash: No Fire: No | Unknown |
| Mar 2026 | ELECTRICAL SYSTEM,ENGINE | I was driving the truck on the freeway and the engine completely shut off with no warning. I pulled to the side of the shoulder and I could smell a burning smell. The truck wouldn’t start back up or move in neutral. Towed it to a shop and they said it had a camshaft issue and a slight knocking noise when they got it to fire up only would run for a little then shut back off. Now I’m having to replace the whole engine due to being bad with the cam code and knocking. | Crash: No Fire: No | Unknown |
| Mar 2026 | ELECTRICAL SYSTEM | The backup camera is too bright at night and therefore useless . Tried searching the web but found no fix that would actually work. Took my truck to the dealer and they never heard of this issue even though there are numerous articles about it on the world wide Web. | Crash: No Fire: No | Unknown |
| Mar 2026 | ENGINE | February 28th 2026, I was driving on the highway with my children and suddenly without any prior warning my cars check engine light came on. It immediately starting losing power, made a knocking noise, and sounded like it was misfiring. Fortunately I was able to make it safely off the highway and have my car towed to the dealership. This was most definitely a life threatening situation which no one should have to face. The dealership dismantled my engine and i was advised the engine had an internal failure due to the valve lifter , rods , and camshaft damage. When looking online there are many complaints and lawsuits regarding this investigation of GMC’s 5.3 engine. I believe this was due to catastrophic damage of the components and there needs to be a recall regarding this issue. The car has always been properly serviced and regular oil changes. | Crash: No Fire: No | Unknown |
| Mar 2026 | ENGINE | While driving, my vehicle experienced a sudden and complete engine failure without any prior warning. There were no warning lights, dashboard alerts, or performance issues that would have indicated an impending mechanical problem. The failure occurred unexpectedly while I was actively driving on a public roadway. After the incident, the vehicle was inspected and diagnosed by a licensed mechanic. The diagnosis determined that an internal engine lifter failed, which subsequently caused damage to the camshaft. This type of failure appears to be the result of an internal mechanical defect rather than any form of neglect or improper maintenance. The abrupt nature of this engine failure created a serious safety hazard. The vehicle suddenly lost the ability to operate normally, forcing me to slow down and stop in active traffic. This unexpected loss of power placed my safety, as well as the safety of other motorists on the road, at significant risk. A critical engine component failing without warning while the vehicle is in operation raises serious concerns about reliability and safety. The vehicle has been properly maintained throughout ownership. All routine maintenance and servicing have been performed by licensed mechanics, and I can provide complete maintenance records documenting this history. At no point prior to this incident were there any signs, warnings, or diagnostic alerts indicating an issue with the engine. The vehicle has already been fully inspected and diagnosed by a licensed mechanic, and the findings are available for review. If necessary, arrangements can be made for the manufacturer or an authorized representative to inspect the vehicle and verify the damage. Given the sudden nature of this failure, the internal engine damage involved, and the safety risk it created while driving, I am requesting that this issue be formally reviewed and addressed by the manufacturer. | Crash: No Fire: No | Unknown |
| Mar 2026 | SUSPENSION | My 2020 GMC Sierra Denali diesel with approximately 90,000 miles experienced two separate front suspension failures within a short period of time. The driver side tie rod and wheel hub failed first and required repair. Shortly after, the passenger side front suspension failed in a similar way and the vehicle had to be towed. These failures caused the front wheels to become unstable and created a serious safety concern while driving. Suspension components such as tie rods and hubs should not fail at this mileage under normal driving conditions. | Crash: No Fire: No | Unknown |
| Mar 2026 | STEERING,POWER TRAIN,ENGINE | Hi, was driving Vehicle GMC 1500 Denali, vehicle Lost power, all Lites lite up on Dashboard, Vehicle Just lost power and i swerved off Road and sideswiped a Plant Holder on side of Road, damaging side passenger Rear door. I bought the truck to GMC Rvc and they said vehicle Blew Cam shaft and Lifters. I explained to them I'm very concerned for others safety in these Vehicles with the 6.2 Engine. Someone is going to get Killed or even a family. I did look up this vehicle its not listed in Recall, but this vehicle has same engine as ones in Recall. Rvc Gmc issued me a bill for repairs for the amount of $8185.20 and they stated they took 3k off invoice. I did Pay total Invoice....I'm just asking you to please look into this as this is defiantly an issue and this year should be listed on Recall as well.. Thanku for at least looking at this. My cell is [XXX] if you need to reach us...Thx.... INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: Yes Fire: No | Unknown |
| Mar 2026 | ENGINE AND ENGINE COOLING | The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving approximately 40 MPH, the check engine warning light illuminated. The vehicle was taken to a dealer, where it was diagnosed, and determined that the oil pump solenoid needed to be replaced. The vehicle was repaired, but after the repair was performed, the engine seized. The manufacturer was notified of the failure. The failure mileage was approximately 45,000. | Crash: No Fire: No | 45,000 |
| Mar 2026 | ENGINE | At 96,000 miles (3,000 miles after the extended warranty expired), I noticed the "GM tick" more prominent and had more of a metallic sound than it ever did. Upon further investigation, it was found that a collapsed lifter may be the culprit. The truck was brought to the dealer and it was confirmed that the #1 hydraulic lifter had collapsed and needed replacement. This work was approved and tonight, I received a call from Rivard Buick GMC saying that the collapsed lifter also caused significant wear on the camshaft which also now requires replacement. Loss of power on the road poses a significant risk as I carry my children in the vehicle. No warning lamps, messages, or other indicators appeared before or when the issue occurred. The issue was reproduced by the manufacturer/dealer. The dealer Service Manager confirmed that this is extremely common with these trucks with the 6.2L engine and said it was a design flaw due to Dynamic Fuel Management, as well as the oil viscosity recommendation from GM being too low. The year group before and after the 2020 has been recalled along with TSB's issued, however, this group is not part of it. I contacted GM Customer Service (Case [XXX]) and was offered a 10% discount on the repair, being told that this is a "great deal considering the vehicle is out of warranty". GM Customer Service has now resorted to not answering any further questions after several attempts to reach someone. This is also after replacing the 10-speed transmission that was also not part of any recall but that was such an issue that the dealer was only able to source used transmissions rather than new parts. Clearly GM won't make the right decisions to back their products or customers, so NHTSA intervention is necessary. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6) | Crash: No Fire: No | Unknown |
| Mar 2026 | ENGINE | The motor went to knocking and lost power. Cost us about 3500. To fix. Lifters went down cam went down which caused major motor knock and loss of payer | Crash: No Fire: No | Unknown |
| Feb 2026 | STEERING,ENGINE | The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at various speeds, the steering wheel became stiff and difficult to steer to the left or the right. The power steering and check engine warning lights were illuminated. The vehicle was towed to a local dealer, where it was diagnosed with a corroded body ground strap. The error codes were cleared, and a test drive was performed. The vehicle was repaired out of pocket. Upon further investigation, the contact related the failure to the GMC Customer Satisfaction Program: N252515590; however, the VIN was not included. The manufacturer was not made aware of the failure. The failure mileage was approximately 37,061. | Crash: No Fire: No Towed | 37,061 |
| Feb 2026 | POWER TRAIN | Vehicle is shifting hard when switching gears. Typical with the recall and the valve body being the issue. Dealership is saying it is not covered by recall. | Crash: No Fire: No | Unknown |
| Feb 2026 | ENGINE | Misfiring due to DFM which is a common issue. Running a scan confirmed. I have installed a AFM/DFM disabler which seems to fix the issue. | Crash: No Fire: No | Unknown |
| Feb 2026 | ENGINE | Have not had my truck in over a month while it’s getting repaired had engine failure sure to faulty hydraulic lifters and camshaft failure due to the Dynamic fuel management system purchased warranty for my vehicle but this needs to be looked into it is unfair as a consumer that they are not doing anything about 2020 models and earlier they are just focusing on 2021 and up. They almost had me crash my truck due to power loss | Crash: No Fire: No | Unknown |
| Feb 2026 | ENGINE | The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, there was a loud rattling sound coming from the engine. There was no warning light illuminated. The vehicle was taken to the dealer, where it was diagnosed with crankshaft failure. The contact was informed that the crankshaft could be replaced; however, the dealer suggested that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure. The approximate failure mileage was 44,000. | Crash: No Fire: No | 44,000 |
| Feb 2026 | SERVICE BRAKES,FORWARD COLLISION AVOIDANCE | The brakes suddenly activate and cause the vehicle to rapidly stop with no warning of any kind and without any braking action being taken by the driver. Then, the brakes do not release and the vehicle cannot be moved as the brakes remain on. Turning the engine off and then restarting it or shifting to other gears does not release the brakes. The vehicle remains immobile and cannot be driven. After a few hours have passed, like overnight, the brakes release and the vehicle can started and driven just as if nothing had happened. A message briefly appears on the vehicle information screen each time this inadvertent braking occurs. It reads, “Brake Failure System”. These brake lockdowns occurred when driving on streets and in the driveway. No accident resulted but could have easily occurred. This is dangerous for a driver and occupants of a vehicle with this safety flaw as well as for other people and vehicles in the vicinity. This has happened five times. The last two instances resulted in the vehicle being loaded onto a tow truck and taken to a dealer of the vehicle’s manufacture. Thus far the dealership has not found what may be causing this intermittent braking problem. | Crash: No Fire: No | Unknown |
| Feb 2026 | POWER TRAIN | The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle unexpectedly sputtered. There was no warning light illuminated. The vehicle was taken to the dealer, where it was diagnosed with torque converter failure. The dealer determined that the torque converter needed to be replaced. The vehicle was repaired. The contact later stated that while driving at an undisclosed speed, the vehicle unexpectedly went into LIMP Mode. There was no warning light illuminated. On several occasions, the vehicle unexpectedly downshifted and lunged forward while stopped at a traffic light. There was no warning light illuminated during the failure. The dealer was contacted. The vehicle was not diagnosed or repaired. The manufacturer was made aware of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 97,000. | Crash: No Fire: No | 97,000 |