GMC Sierra Complaints (2020)

626 consumer complaints on file.

#11734729April 30, 2026
ENGINE
On 6/27/22 my 2020 gmc sierra 1500 at4 6.2L had lifter failure. The dealer fixed that problem and on 7/1/22 again has lifter failure. The dealer fixed that problem again. On 7/13/22 a third time engine had lifter failure again. I requested they need a different engine to be installed and GM agreed andthey install an L87 2022 engine. This engine seemed weak and not right since it was installed. On 10/13/222i took the vehicle in to the dealer with a complaint of ticking noise from engine area and complaint of shifting hard. The fix the shifting but nothing was wrong with engine according to the dealer. On 3/15/24 the noise are worse and I can smell fuel and noticed white milky residue on the oil cap plus a growling nose coming from engine. Coolant keeps going low and white smoke out the exhaust. The dealer does diagnosis and again nothing is wrong. Now starts the oil consumption testing and me letting the dealer know that I can smell oil and exhaust but they can't. On 8/29/2024 I take truck in for another diagnosis for rattle sounds I'm hearing under the hood from the engine especially when you accelerate. I pay $149.49 for the dealer to find the noise and they tell me they can't find anything, but everyone who has rode in the truck can. On 1/27/2025 I take the vehicle in again and the dealer does the valve cover leaking and replaces that is covered. On 2/3/2025 again vehicle back to dealer cause I can smell antifreeze and burning oil smell. The only thing they found was the muffler had a Lil leak so they wanted me to get it welded which i did and so can smell the oil. On 6/16/2025 I take the vehicle in for oil change and leave to go home then go to work about 95 miles or more and noticed after I parked and was working before I was going to head home there was a huge puddle of oil under the vehicle. I took pics. Found after inspecting my vehicle the oil cap was not in filer tube but instead sitting up on air shelf above radiator. Oil filter was about 3 turns loose.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11734885April 30, 2026
ENGINE, POWER TRAIN
I’m scared to drive my vehicle because of the 6.2L V8 ongoing engine failures! I believe it to be unsafe for travel never knowing when the engine will fail. Now with over 1 Million failures of this engine!
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11734522April 29, 2026
ENGINE
Driving on highway, engine light came on with many warning lights. Was just starting on a trip to SC then OH to help father for a surgery. Lifters went bad within fist 5-6k miles on the truck (6.2L) causing other damage to the engine such as bent rods (etc). Dealer repaired all DFM Lifters as there were failures on both sides of the engine, but it still sounds like there are issues internally. It is a 2020 manufactured in 2019, I have not had additional mechanical issues, but I have purposely not driven it as much since I feel that it is not dependable. It currently only has about 27k miles and sounds worse than my 2007 Lexus engine with 180k+ miles. I wanted to fill this out, so you have the data for the engineering investigation.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11734531April 29, 2026
ENGINE, SERVICE BRAKES, VEHICLE SPEED CONTROL
The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle decelerated to 30 MPH. The check engine warning light was illuminated. The vehicle was taken to a local dealer, where it was diagnosed, and determined that the timing belt needed to be replaced. The part was on back order. The vehicle was not repaired. The contact stated the vehicle previously experienced brake failure, sensor failure, and glow plug failure. The manufacturer was contacted, but no assistance was provided. The BBB referred the contact to the NHTSA Hotline to report the failure. The failure mileage was approximately 80,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11733580April 24, 2026
ENGINE
My 2020 GMC Sierra 6.2L (only 46,000 miles which is under warranty mileage criteria), suffered catastrophic engine failure while at 40 miles per hour out of no where and rolled without power for about ~60ft. Power came back on, and I was able to get closer to the dealership but again, lost all power and rolled for about 60ft again right in front of the dealership. The truck died while attempting to make a left turn (in oncoming traffic), it got going again in time to finish the turn. When I pulled into the dealership it pulled code P0016 which is the same code for the 2021-2024 recall currently for the 6.2L GM engine. I had all oil changes completed on time and can show evidence of them. Other repairs, recalls etc were completed at the GMC dealership. The 2020 Sierra 6.2L should absolutely be included on the GM recall. Same issues as 2021-2024. Funny how 2020's just reached over on time limit for warranty. The repair estimate for my truck is over $13K!!!
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11733360April 23, 2026
ENGINE
I took my 2020 GMC Sierra in for an oil change. The engine seized when it the technician tried to restart the car. We had it towed to GMC where they confirmed the engine seized. The oil repair shop then replaced the engine and when doing so confirmed the original threw a rod which is the same recall issue that is occurring with the 2021-2024 models. I have since taken the car to GMC for a full inspection and made additional repairs. The vehicle is available for future repairs. My safety and others are at risk as the engine could seize leaving my family stranded or endangering others on the road if the seizure occurs while driving. Yes the vehicle was inspected at the GMC dealership and the shop where the engine was replaced with another L87 engine. there was no warning the engine seized after an oil change.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11733029April 22, 2026
ENGINE, ENGINE AND ENGINE COOLING:ENGINE:CRANK/CAMSHAFT POSITION SENSOR
The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed 60 miles away from home, the vehicle lost automotive power and stalled. The contact stated that the vehicle started smoking. Several unknown warning lights were illuminated. The vehicle was taken to a local dealer, where it was diagnosed and it was determined that the failure was due to an internal failure with the camshaft and the engine. The vehicle was not repaired. The manufacturer was contacted and referred the contact to the local dealer for assistance. The failure mileage was approximately 167,570.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11732880April 21, 2026
ENGINE, POWER TRAIN
After owning this truck a little over a year I’ve had to replace the transmission and now it’s in the because the motor sounds like a bag of marbles was put in it and the warranty company is a joke they only want to replace just the cam and lifters but yet the dealership hasn’t be authorized to go to the bottom of the motor to check it out this truck has been nothing but a lemon!!!!!
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11731599April 16, 2026
ENGINE
While driving on the highway, my engine failed unexpectedly and I had to coast across the highway without power. I had the vehicle towed to a GM dealership, where I was informed the failure was due to a lower-end engine issue and that a full engine replacement was necessary. I am aware of known issues with GM’s 6.2L engines and asked the dealership about the related recall. They acknowledged that the failure I experienced is consistent with the symptoms seen in the defective 6.2L engines. However, they stated that because my truck is a 2020 model, it does not fall within the affected VIN range. I ultimately paid nearly $11,000 for a new engine. Given the nature of the failure and its alignment with known issues, it is difficult to believe this was merely coincidental. I strongly believe the same defect exists in my engine, despite it not being included in the current recall range.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11730820April 13, 2026
ENGINE
There is a click/ticking noise when vehicle is started. Noise gets louder and faster when accelerating. Have taken vehicle to 2 mechanic shops and been told by both places it is bad lifters and exhaust manifolds. I took this truck in because of loss of power. This issue has put me in unsafe/ dangerous positions on multiple occasions.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11729751April 7, 2026
ENGINE
The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the vehicle went into LIMP Mode, and several unknown warning lights were illuminated. The vehicle lost automotive power. The vehicle was taken to the dealer to be diagnosed. There was a knock coming from the engine, there was fuel injector failure, a heated oxygen sensor control module Bank 1 failure, and fuel system failure. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 134,648.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11729552April 6, 2026
ELECTRICAL SYSTEM
Infotainment screen is flashing different colors and doesn’t work anymore.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11728804April 2, 2026
ENGINE
When the truck was idling the dod/afm turned on and disabled a cylinder and now I’m just having codes pop up for cylinder misfires
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11727414March 27, 2026
POWER TRAIN
The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving on several occasions at various speeds, the vehicle started shaking and slipped in and out of gear, with the message "Idle Transmission" displayed. The vehicle was pulled over and shifted into park(P) and then to drive(D). There was a loud banging sound coming from the rear of the vehicle. The vehicle was towed to an independent mechanic, where it was diagnosed with transmission failure. The contact was informed that the transmission needed to be repaired. The vehicle was not yet repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 80,000.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11726877March 24, 2026
ENGINE
My engine started knocking horribly, I need to get a proper diagnosis but cannot afford to have a shop look at it. I have been building engines my entire life and am certain the rod bearings have failed. The engine has a distinct knock under acceleration, you can hear it clearly when pulling away from a stop sign for example.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11726286March 23, 2026
ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL:UREA INJECTION SYSTEM (DEF), VEHICLE SPEED CONTROL
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
Injuries:
0
Deaths:
0
#11726349March 23, 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
Injuries:
0
Deaths:
0
#11726576March 23, 2026
VISIBILITY/WIPER, STRUCTURE:BODY, UNKNOWN OR OTHER
The frame of the back window is cracking allowing water to come in through the back glass. This is causing the headliner and other components such as air bags and other electrical components to get wet and damaged. This could cause risk of fire or failure of safety components within the vehicle such as air bags, cameras and other sensors. With water intrusion comes the high risk for mold to develop and cause serious health risks. GMC is aware of this issue and will not agree to repair it. A GMC dealer has inspected the glass and said it was a faulty seal but since it's not in the 3 year warranty window, it's not covered. Independent auto glass companies state they have seen this issue many times and the glass seal is faulty. GMC should do the right thing and fix this issue. This devalues the vehicle and the GMC brand and poses serious risks to driver. I have created a case with GMC and submitted photos, videos and dealership estimates for proof.
Crash:
No
Fire:
No
Injuries:
0
Deaths:
0
#11726088March 21, 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
Injuries:
0
Deaths:
0
#11725751March 20, 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
Injuries:
0
Deaths:
0

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