2020 GMC Sierra 1500: hesitation when accelerating

Filed Jun 10, 2026 · Transmission · 88,000 miles · CO

The contact owns a 2020 GMC Sierra. The contact stated while driving at an undisclosed speed, the transmission hesitated and shifted unusually rough. No warning lights were illuminated. The vehicle was taken to an independent mechanic where it was diagnosed with a transmission valve issue. The contact was advised that the power train software needed to be updated. The contact was informed of an unknown recall; however, the VIN was not associated with a recall related to the failure. The vehicle was not repaired. The dealer was made aware of the failure. The manufacturer was not made aware of the failure. The failure mileage was approximately 88,000.

Filed May 29, 2026 · Engine, Fuel system · FL

I again have noticed intermittent pulsing at low to medium speeds. At roughly 1k-2k rpm the engine at or about 10-20 mph is pulsating or hesitating with an obvious pulse which you can see on the tachometer as well (bouncing.) It seems like there is either a computer, fuel flow or electric issue. Also, at speeds up to the 40 mph range, this is happening as well. Yesterday while towing a small 7'x12' empty dual axle trailer I noticed it again, I occasionally use my trailer to haul small loads up to 4500lbs. This has happened before but this time I decided to notate this on your site, since reading about ongoing problems with the 2020 6.2L GMC Sierra 1500. I was aware of the other following years, 2021-2024? issues and that is why I purchased this 2020 year model. My truck will be available for inspection when the request is sent to me. Safety was not an issue, I ran my truck most of the day. I have not yet notified my Chevrolet dealer, Roger Dean, Cape Coral, FL. My truck has not yet been inspected for this issue. There were not any lights or warnings on display at time of incidents. Thank you, [XXX] [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Mar 18, 2026 · Engine · 121,000 miles · TN

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.

Filed Jan 19, 2026 · OK

Transmission 10l80 stuck solenoid truck has hesitation delayed shifting. And will not shift after certain gears.

Filed Oct 15, 2025 · Transmission · 75,200 miles · FL

The contact owns a 2020 GMC Sierra 1500. The contact stated while driving approximately 40-60 MPH, the transmission hesitated while depressing the accelerator pedal. A dealer was contacted. The vehicle was taken to the dealer and was diagnosed with transmission control module (TCM) failure. The contact was informed that the TCM needed to be replaced. The vehicle was not repaired. The contact related the failure to the federal safety agency Campaign Number: 24V797000 (POWER TRAIN); however, the VIN was not included in the recall. The manufacturer was notified of the failure and referred the contact to the federal safety agency Hotline to report the failure. The failure mileage was 75,200.

Filed Dec 4, 2024 · Acceleration, Fuel system · LA

Shuttering while in motion at a speed of 35mph or above. My 2020 GMC SIERRA 1500 AT4 CarbonPro while driving at or above speeds of 35mph experiences a hesitation and severe Shuttering while trying to maintain any speed of 35mph or above. The hesitation causes extreme vibrations and hesitation when lifting or applying foot to the accelerator. This happens in any drive mode also with cruise control on or off as well as shifting into low and being in any gear trying to prevent it. It also does this on any road and condition. It feels like a slip in the transmission or torque converter, possibly could be the rear end or variable valve timing as well. And when taking of from a red-light or stop sign it slips as if the truck has lost traction, but it hasn't. This is very dangerous and could be the cause of a serious accident when trying to accelerate. If your traveling at hwy speeds it feels as if the brakes are being applied and the tires are going over a washboard which could cause a collision, tire wear, or driveline damage.

Filed Oct 23, 2022 · Transmission · TX

My 2020 Sierra SLT always hesitates or stutters upon take off only on the very first start of the day every day. It appears to be a transmission gear issue or perhaps air/fuel issue. I also have had several different issues with my infotainment system. It screen changes from one screen to another on its own occasionally and it also has a very loud pop when I turn off my iphone Xr from the trucks sound system as if it will crack my speakers. I have taken it in to two separate Cavendar GMC dealerships in San Antonio on 3 different occasions and they claim it does not do either. This cannot be the case as it does it for me every single day since I bought it from the showroom floor. They have said they have updated or reprogrammed both systems but I still have both issues. I am about to lose warranty coverage and I am afraid this will never be addressed. I am taking it in 1 last time. I will never buy another GM product!

Filed Jan 14, 2021 · Driver assistance, Engine · 3,800 miles · TX

Within 3 months (<4000 miles) from purchase vehicle began sputtering with hesitation, and ticking noise from engine while in motion followed by multiple alerts posting on driver display. Vehicle displays loss of power, and struggles to keep up with traffic. Check engine light flashing followed by constantly staying on, service ESC system activated, service parking brake, and steering assist reduced drive with caution lights all activated during this episode. Dealer worked on vehicle engine ( and completed on or around 1/08/2021), and replaced lifters, and oil control valve. On 01/13/2021 noticed that vehicles lane keep assist is now working sporadically, will not activate consistently when vehicle veers off the properly marked lanes on high-way/roads, and inconsistently alerts driver while in motion. The lane keep assist is suppose to correct steering, but this does not happen consistently. The collision alert system does not activate or work correctly. Noticed while driving that vehicles in front are not detected correctly, and informs the driver they are within safe distance (green this suddenly changes to yellow). In addition when vehicles in front apply brake, the collision alert system does not alert as it is supposed to, it stays in green even at extremely close range. Safety mechanisms don't appear to work correctly, and detects items that are not present. Noticed that vehicle detects lanes even on unmarked roads, and the front pedestrian alert system activates sporadically even if no pedestrians are in front of vehicle while driving. Concerned about safety features leading to hazardous driving conditions.

Filed Dec 30, 2020 · Brakes, Transmission · 5,000 miles · NJ

Car was idling and parked. Warning code showed up on dashboard ESC, electronic stability control, reduced engine power. Vehicle then displayed transmission disruption, warning light displayed as well. I was able to drive it to the dealership but the performance of the vehicle was limited by the reduced engine power. Transmission was hesitating and clunky during gear changes. My sierra has 5,000 miles on it and the transmission was already replaced at 2,000 miles. Gmc has a serious problem with this make and model. Unsure what the resolution will be, but I am no longer confident in the product gmc is selling.