GMC Sierra Complaints (2020)

626 consumer complaints on file.

#11759726August 26, 2026
STRUCTURE:BODY
I have a rear sliding window on the cab of my truck that leaks from both ends of the plastic guide. I noticed it when placing my young children in their car seats. I contacted my dealership and was informed the repair would cost $1500+ and not be covered by GM or warranty.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759731August 26, 2026
ENGINE
On XXX my GMC 6.2L Sierra 1500 Denali engine cutoff in Traffic and had to be towed. There was no indications prior to failure. Found out after replacing battery that the 400amp fuse blew and the engine seized. Vehicle was then towed to Hendrick Buick GMC dealer in [XXX] for repair. My engine has 49,500 miles but is out of warranty due to time. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759795August 26, 2026
ENGINE
Misfire on 2 cylinder, noise on start up diagnostic code P0300 P0302 P050 I was driving home and the engine started making a strange sound, vehicle would could no increase speed normally. The dealership did basic analysis from the onboard computer and did a compression test. Heavy knocking sound on passenger side of the engine. The issue happened on Aug 5th 2026. The issue is due to the AFM that causes the lifter to fail and dealership says I need a new engine $15787 or replace cam shaft $14530.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759816August 26, 2026
POWER TRAIN, UNKNOWN OR OTHER, VEHICLE SPEED CONTROL
This truck was bought brand new by my father. Around 38,000 miles it begin having issues with shifting which eventually got worse. When I searched google for issues many others on different pages have had the same issues. The shifting would be so rough it feels like you're being hit by another vehicle. This could cause accidents for anyone who cannot afford to fix these known issues by GMC. I was told today by my local dealership their transmissions for my specific truck is on backorder. Should that not indicate an issue when this truck is a 2020. But to my father having a stroke I was not able to handle this issue sooner as he was very ill for four years and passed last year. The truck was not the priority at the time.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759601August 25, 2026
ENGINE
Engine went into limp mode and engine is no longer good
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759035August 24, 2026
ENGINE
I purchased my 2020 GMC Sierra 1500 AT4 with the L87 6.2L V8 new from a GMC dealer in March 2020 for $65,910 (VIN [XXX]). The truck has primarily highway mileage, very little towing, and has been well maintained. At 166,634 miles on [XXX], the truck developed a flashing check-engine light. The GMC dealer diagnosed “Cyl 3 lifter failure with camshaft damage” and determined that replacing the engine was preferable to repairing it because of the vehicle's mileage. The dealer installed a replacement OEM GMC engine and replaced both broken engine mounts. The replacement engine and installation cost $11,778. The replacement engine has subsequently required multiple repairs. At approximately 170,411 miles, the GMC dealer documented an exhaust leak that had occurred since the engine repair and a coolant leak from the upper radiator hose; both were repaired. At approximately 187,699 miles, the truck experienced overheating, coolant leakage, and loud engine-area noise. The dealer found that the water pump was coming apart and replaced the water pump and related components. I am reporting this vehicle because it is a 2020 Sierra equipped with the L87 6.2L engine and experienced catastrophic lifter/camshaft failure requiring complete engine replacement, followed by multiple engine-related repairs. I believe this history is relevant to NHTSA's investigation of L87 engine failures in earlier model years and warrants consideration when evaluating whether the known L87 engine defect extends beyond the vehicles currently covered by the recall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759239August 24, 2026
ELECTRICAL SYSTEM, ENGINE, POWER TRAIN
Our 2020 GMC SIERRA 1500 has suffered catastrophic systems and engine failure including the brakes multiple times for almost 4 years. It has happened in high traffic and on the interstate each time having to be coasted off of the road to come to a rolling stop. There have been nine repair attempts with GM dealers repeatedly stating the issues were repaired and returning our vehicle to us. We began making the CEO and Executive team aware of the potentially deadly safety hazards including the fact that I, [XXX] am disabled and power wheelchair dependent requiring a truck that can carry my power wheelchair. We have sent numerous emails to Ms. [XXX] and the Executive team numerous times informing them in detail, each time, of all issues involved. We started communicating via phone and email with customer care to no avail. All attempts at repair finally ended in complete engine failure leaving us with an estimate to replace the engine of over $13,000. We have also, submitted a detailed complaint to the Attorney General’s Office and after review were given the Case # TCP - XXX. I will attach the Complaint and Addendum sent to the Attorney General along with two of the emails sent to Ms. [XXX] and her team informing her of all issues with the truck. They took no action to actually help us get this truck off of the road knowing it was having catastrophic engine and system failure and that it had to be driven to transport a disabled power wheel dependent with severe medical issues and the medically necessary power wheelchair. I am also attaching the earliest OnStar Diagnostic notice of Engine, Transmission and Emissions system issues from May of 2023. The issues have remained the same from the beginning only worsening though my husband has only driven the truck in town on slower less busy streets learning how to make adjustments such as pumping the brakes and starting and stopping the truck to keep it going. My carrier is installed and yet it is undrivable. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATIO
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11759264August 24, 2026
ENGINE, BACK OVER PREVENTION: REARVIEW SYSTEM BRAKING, BACK OVER PREVENTION: WARNINGS
Piston 5 dropped compression to 120 the rest were 190-200. The engine failed therefore none of my parking assist sensors were working and I backed into a car because the truck was misfiring.
Crash:
Yes
Fire:
No
Injuries:
0
Deaths:
0
#11759295August 24, 2026
POWER TRAIN, ENGINE
The 5.3L Engine active fuel management failure problem. This known problem with the GMC motors was not disclosed by any dealerships or the manufacturer. While driving down the roadway, the truck had an engine malfunction and I was fortunate enough to be able to safely pull over. The check engine light activated and I took it to the dealer the next day. I was informed by the dealer that this was a known, common issue that GM was aware of but was not offering assistance. I had to pay $11,000 out-of-pocket because of this.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11757361August 17, 2026
FUEL/PROPULSION SYSTEM
Gas fill door won’t stay closed
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11756301August 11, 2026
ENGINE
I was driving doing about 60 mph. All of a sudden the engine stopped and the truck just coasted. I was able to find a safe spot on the side of the road and pull over. Called a tow truck and had it taken to the GM dealership nearby. The trucks engine was just fixed in October of 2025 for the camshaft and lifter rods. It’s currently in the shop and I’m waiting for the diagnostics.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11755269August 6, 2026
ENGINE, POWER TRAIN
"While driving, the vehicle suddenly experienced a flashing check engine light, an Electronic Stability Control (ESC) warning light, and violent steering wheel vibrations. The vehicle suffered a severe loss of power and misfired, creating an immediate traffic hazard. The dealership diagnosed the issue as a catastrophic mechanical lifter failure on the 5.3L V8 Ecotec engine with Dynamic Fuel Management (DFM). Despite the dealer replacing an entire bank of lifters, the engine continues to misfire and vibrate. This premature valvetrain failure at only 36,000 miles is a known design defect that causes sudden engine stalling and disables critical safety features like stability control while the vehicle is in motion, presenting a severe crash risk."
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11754824August 4, 2026
ENGINE
The truck starting making a ticking noise within 24 hours the check engine light was on and it starting shuttering. I got it to the dealership were they informed me of lifters failure, and catastrophic engine failure. Dealer is recommending replacing engine since it's a 2020 and not part of recall.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11754382August 3, 2026
ENGINE
I brought my truck into a certified GM dealer for recall work on the ground strap. I left the dealership and multiple lights came on dash: check engine light, service ecs, traction control, service parking brake, steering assist reduced. 7 minutes later the engine began miss firing. The dealer asked me to bring it back to the shop and after some digging they discovered my L87, 6.2 engine was missing firing in cylinder 5. Now the motor needs to be replaced and GM is not standing behind the repair.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11754596August 3, 2026
POWER TRAIN
My truck shudders when driving. It has 78,000 miles on it. It started shuttering around 73,000 miles. I baby my truck and don't do switch backs or hot rod around.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11750977July 17, 2026
POWER TRAIN, SUSPENSION
My truck transmission beed jerking off and on for over a year. One time it lose power when i was driving and could have caused an accident. I took it to the dealership and they said i new a new transmission for $12000. Something just doesn’t seem right about this! I brought a brand new truck thats unsafe and its no recall for my model but other models with the same issue had a recall. I would just like some answers. I feel like i brought a lemon. Thanks for listening.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11751171July 17, 2026
ENGINE, SERVICE BRAKES
The contact’s mother-in-law owns a 2020 GMC Sierra 1500. The contact stated that while her brother-in-law was starting the vehicle, the brake, service engine, and engine warning lights illuminated and the vehicle failed to start. The contact stated that the failure was associated with NHTSA Action Number: EA25007 (ENGINE, ENGINE, AND ENGINE COOLING) and PE25001 (ENGINE, ENGINE, AND ENGINE COOLING). The vehicle was towed to a local dealer, where it was diagnosed with engine failure. The vehicle was not repaired. The owner was scheduled to meet with the dealer to discuss the issue. The manufacturer was contacted and confirmed that there were no open recalls on the VIN related to the failure. The failure mileage was approximately 45,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11749070July 8, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2020 GMC Sierra 1500. The contact stated that while accelerating from a complete stop on several occasions, an abnormal clicking sound was heard from the engine compartment. The vehicle was taken to the dealer, where it was diagnosed with a failed fan belt pulley. The vehicle was not repaired. Additionally, while parked on one occasion, an abnormal clicking sound and a loud bang were heard from the engine compartment, and the vehicle stalled. The contact attempted to restart the vehicle, but it failed to turn over. The vehicle was taken to the dealer, where a failed valve spring was diagnosed. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was approximately 75,127.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11748595July 6, 2026
ENGINE
The cam shaft bearing failed under normal driving conditions. Many of the service engine lights including brakes and primary service engine light came on after the cam shaft bearing failure. The engine was replaced by a GM dealership at 65,000 miles and was inspected to determine the cam shaft bearing failed. Luckily the engine failed at a speed of 35 mph on an off ramp, as a complete engine failure on the highway could have been much more dangerous. Following the replacement of the engine, within 500 engine miles, O2 sensors in the catalytic converter were replaced and ultimately the catalytic converter had to be replaced as well.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11747347June 30, 2026
ENGINE AND ENGINE COOLING
The contact owns a 2020 GMC Sierra 2500. The contact stated that the check engine warning light was illuminated, and the message "Reduced Power" was displayed. The vehicle was taken to the dealer, where the turbo actuator and wastegate position sensor A-circuit were replaced; however, the failure persisted. The vehicle was taken back to the dealer, and the contact was advised that another diagnostic test was needed. The contact declined to pay for the diagnostic test. The vehicle was taken to a retired GM mechanic, who diagnosed the vehicle with turbo charger failure. The vehicle was not repaired due to the cost. The manufacturer was notified of the failure, but no assistance was provided. The failure mileage was approximately 100,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0

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