2020 GMC SIERRA 1500 Complaints

-Transmission valve body Failure, Wheel lock up, ABS Event, Loud Bang and a Flashing "D" on Driver Information Center (DIC) when Lightly or Moderately Accelerating Forcing an 8-7 or 8-6 Downshift -When all four tires lock up at a high rate of speed, this puts the driver, the passengers, and all others on the road at risk for injury or death. -Yes, the problem has been found in a document by my local dealer that this issue was added to my exact vehicle's service manual on 11/27/24. The document describes in detail the exact scenario I have been involved in multiple times. It is deemed as #21-NA-275. It locks up the tires randomly to the vehicle in mid acceleration at any speed including 80 miles per hour in one instance for me. -Yes, the dealership inspected it and found the issue to correlate with the newly added section to the service manual, 13333166. This document ID is 5925530 and the added information to the dealership is #21-NA-275. The GMC manufacturer has been contacted as of 3PM MST 3/14/25. Insurance doesn't deal with mechanical problems. The police will only be involved when there is death or injury. -No. The only warning that happens is simultaneously as the vehicle locks up the tires causing the driver (me) to inevitably try to save myself and others, swerving and trying to focus on not hurting myself or others but I did notice the "D" flash on one of these occasions. This is the most dangerous issue with a vehicle I have ever even considered. At any time, for any reason, all four tires can lock up at any rate of speed and cause multiple casualties. The way to fix this is to spend $3,000 which I am sure many people like myself do not have. This means there are thousands of these exact make and models of vehicles on the road right now. Please do not take this lightly as I have almost crashed multiple times with people in my vehicle due to no fault of my own.

The contact owns a 2020 GMC Sierra 1500. The contact stated while accelerating from a complete stop, the vehicle lunged forward. The contact stated that the failure recurred while driving at various speeds depressing the accelerator pedal, and while decelerating to come to a complete stop. The check engine warning light was illuminated. Additionally, the contact stated that while coming to a complete stop at a traffic light, the vehicle lunged forward violently, as if the vehicle had been rear-ended. The vehicle was taken to Quality Plus Automotive, where it was diagnosed that the transmission had failed and needed to be replaced. The local dealer, Leith GMC (919) 366-1000), and other dealers were contacted and informed the contact that an estimate for the repair could not be provided because the transmission part was not available. The vehicle was repaired by Quality Plus Automotive. The manufacturer was notified of the failure and referred the contact to the NHTSA Hotline for assistance. The failure mileage was approximately 75,450.

The Transmission cooler lines broke and spilled out all the oil/fluid on my 2020 GMC Sierra Elevation pick-up truck. Once all the fluid was spilled out the Sierra truck would no longer move. The Sierra truck was towed to the dealership I originally purchased the vehicle. The dealership was Cranbury Buick GMC. The dealership mentioned that the hoses broke/leaked from the crimped housing at the ends of the hoses. The dealership stated that the original OEM transmission cooler line hoses were discontinued and new OEM replacement transmission cooler line hoses were created. Please see the attached dealership bill/invoice for the parts and labor to fix the cooler line issue. I feel this issue should be a recall on all 2020 GMC Sierra trucks, especially if GM replaced the original OEM hoses with newly created OEM hoses Thanks [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The contact owns a 2020 GMC Sierra 1500. The contact stated while driving at an undisclosed speed, the parking brake was independently activated. In addition, the contact stated that the vehicle had an oil leak from the oil pan. The contact stated that the oil needed to be added every two days. The contact stated that the alert system warning light was illuminated. The vehicle was taken to the dealer; however, the failure was not duplicated. The contact was informed that the failure could not be duplicated, because no active codes were retrieved. In addition, the contact stated that the frame had corrosion. The vehicle was taken to the dealer for corrosion failure, however, the contact stated that the previous dealer had failed to help. The dealer confirmed the corrosion; however, the vehicle was not repaired. The manufacturer was made aware of the failure but provided no assistance. The contact was advised to contact the NHTSA Hotline to report the failure. The failure mileage was approximately 10,000.

Had GMC (Leominster, MA), perform the safety recall for the transmission on my Sierra. This is the one for the rear wheel lockup that requires a software update. My battery was completely dead after the vehicle sat for a week. No accessori s plugged in, and it's a 6 month old battery Battery tested fine and is charging now, but it appears the CPU never fully powered down after the software update, resulting in needing multiple jump starts and 3+ hours of run time to charge the battery enough to turn over on its own. I can see this being a safety issue in relation to the Auto-start, because when it is being used, the battery is needed to restart the engine. This could result in a stall at an intersection, and if drivers are not alert, may collide with a stalled vehicle.

Lifters failed and cam shaft was busted. Standard issues with 6.2L engines. Was traveling down highway and vehicles was shaking violently. Inspection report available. Has been inspected by GM service center. No symptoms or warnings prior to failure.

While driving on interstate transmission would “lock up” momentarily creating drastic drop in speed and unable to shift gears and accelerate. “D” would start flashing in dash board. Dealership said this is unrelated to current recall about rear wheels locking up from valve body failure and instead this is an electrical issue. Dealership also stated this is the 2nd truck in a week they have had come in with this issue. Almost caused accident on interstate with my family and I as a result of sudden drop in speed and unable to accelerate with multiple cars behind us.

Tailgate opened on highway with cargo in bed. Also tailgate opens randomly when parked. This has happened many times, creating very dangerous and unexpected situations Numerous contacts to the manufacturer have been unsuccessful in getting the hazard placed on recall. Numerous incidents. Keeps happening

My engine has had continual random piston misfire issues, I have changed the spark plugs, fuel injectors, and cat converter. The vehicle has "dynamic fuel management" (DFM) where four of the cylinders turn off when the load on the engine is low and turn back on when the load is high. A mechanic reviewed the vehicle and determined that all eight cylinders are turning off while driving due to the DFM. When it misfires there is momentary loss of power that potentially puts others at risk. A dealership performed a repair per a Bulletin but the issue was not fixed. The mechanic indicated this is a software issue with the computer update per the Bulletin. I have installed a DFM disabler to prevent DFM from working, don't have misfires, but this is an engineering issue that GM hasn't/won't address.

I went to start my truck after going into the store and the Service Power Steering ESC warning came on and I had no power steering. This is a very dangerous situation without power steering in the vehicle and someone is bound to get seriously injured if this happens while they are driving. I have read numerous threads on this same issue and it does not look like GM has taken this into accounty by recalling all these vehicles with this same exact issue. While most complain that when they take it to the dealership, they cant find any error codes, or when the replace the modules it starts creating more issues with other electronics. GM needs to take care of this issue with the power steering module so the safety of their drivers is not compromised.