general problems of the 2020 GMC Sierra 1500 - part 1

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.

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).

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.

On Friday, January 30, 2026 while driving our 2020 GMC Sierra 1500, we experienced sudden loss of power and the motor making a faint rattling noise. The motor soon after began making a horrible sound - - it was obvious something was very wrong. This vehicle only had 31,995 miles on it at the of the issue. We had the truck towed to the dealer the following day for evaluation. Upon inspection, it was determined that the #5 lifter had collapsed and the left bank of lifters needed to be replaced at an estimated cost of $4500. There were no warning lamps or alerts on our app for over 24 hours. Once at the dealer, we explained to the service advisor that our research concluded that gm is fully aware of these issues and that they are under investigation for possible recall. Our service advisor then made a call to gm who agreed to cover this repair under warranty (which we appreciate and feel was the right thing to do). However, after additional research, we are concerned that the right bank of lifters will fail next, or even worse, catastrophic engine failure that gm will refuse to cover. It is our understanding that ntsb is aware of these issues and is in the process of conducting an investigation. I would like to have our issue added to the investigation.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while his wife was driving at an undisclosed speed, the vehicle jerked violently. The driver stated that the vehicle failed to respond as intended while depressing the accelerator or brake pedal. The check engine warning light was illuminated. The driver was able to pull over to the side of the road. The vehicle stopped jerking while driving but failed to exceed 30 mph. The driver pulled into a parking lot and parked the vehicle. The contact was made aware of the failure and went to the parking lot. The vehicle was restarted and jerked abnormally. Additionally, while shifted into reverse(r), the vehicle failed to function as intended. The vehicle was taken to the dealer, where it was diagnosed, and two dtc were retrieved for unknown transmission software failure, and it was determined an unknown part in the transmission had failed. The dealer informed the contact that an unstated recall was closed. The vehicle remained at the dealer unrepaired. The manufacturer was made aware of the failure, a claim was filed, and the contact was informed that the recall was closed. The failure mileage was approximately 146,000.

I was driving my vehicle on the highway when the transmission suddenly gave out with no warning whatsoever. When I say gave out, I mean, it just completely stopped working and was unable to go into any gear. I was luckily able to coast over to the median without an accident occurring, but it was not without much concern or worry as traffic moving on the highway is 70 miles an hour plus and quite full of vehicles . I consider myself lucky that I have extensive driving experience and was able to conduct myself calmly under the circumstances. It was a bit tricky, getting situated though under those circumstances. There was no advanced warning in anyway. No engine lights, no sounds ,nothing. This is a well maintained vehicle. All my service is done by the dealership, and I have never been given any indication that there was something wrong. However,after this happened, I have been researching and found that many of these vehicles with this transmission continue to have this problem. This is not normal wear and tear or normal mechanical failure. I have owned many vehicles and never felt as unsafe as I did in that moment, or had a vehicles transmission fail so abruptly. For me, and the research I have done, I can only hypothesize the materials and engineering involved with this transmission are inherently inferior, completely faulty, and a safety risk/hazard to anyone who owns or operates the vehicle. I consider myself lucky to walk away unscathed, other than the economic price that it is going to incur on my finances for repairs. I would hope that it doesn’t take something serious to happen before someone takes action and conducts a recall of this product. From what I have read and what I have experienced, this is truly an unfortunate accident waiting to happen and it appears nothing is being done. I truly hope that you could take a little more look into this matter. Thank you for your time and energy. I have already contacted the manufacturer and felt ignored.

My engine is projecting a ticking sound. Oil consumption is extreme.

While driving on the interstate at 70 mph, the transmission began to shudder. It continued the duration of the trip of 90 mins. Following day, the transmission is continuing to shudder and is now shifting hard.

My 2020 GMC Sierra 1500 experienced a premature transmission failure consistent with gm’s known 8-speed transmission defect. My safety and the safety of others were put at risk if/when the transmission occurs a temporary lockup which can/will cause the vehicle to stall on the highway, and potentially create a minor/major automobile incident if vehicle stalls. The vehicle was taken to dealership capital Chevrolet montgomery, al where dealership technician diagnosed/confirmed the issue along with pictures of internal transmission failed components as well as recommended resolution for fix. The vehicle has been inspected by my out-of-pocket expense extended warranty company endurance warranty services sub-contracted repair claims adjuster. No warning lamps, vehicle messages, or other symptoms of the problem prior to the failure were noticeable; the vehicle had multiple diagnostic scans prior to original sale and after sale to present no issues or trouble scans. The first issue appeared or was noticeable 12/08/2025. Gm has refused action by asserting warranty expiration despite widespread knowledge of this defect. The vehicle has been out of service since December 8, 2025.

My 2020 GMC sierra with a 5. 3l engine and 78,272 miles on the vehicle, experienced damaged lifters which also resulted in a damaged cam shaft. The total repair bill was $9,208. 86. While in the GMC dealership for repair, there were 2 other trucks - same model, same year, same engine - in for the same repair. When searching on-line, I found the recall for the GMC 6. 2l engine for similar issues. It is my opinion that the 5. 3l engine is experiencing the same types of issues. I have driven GMC trucks for almost 40 years and have never experienced these types of issues. I have been told by several people that it is related to the dynamic fuel management system and to fix the problem to disable the system to keep the truck in v8 mode. There are several solutions on line to make this happen. I am no engineer and only provide this as background information. From my perspective, it is clear that gm has a problem (whatever the root cause) with their 5. 3l engines.

My truck had engine failure while at the dealership getting new tires installed on 11/12/2025. When they started my truck they detected major knocking in my engine the 1st thing in the morning. It unsafe to drive they're telling me my engine needs to be replaced. My engine has 58,000 miles on it. There was no issues with my truck when I drop it off.

My 2020 5. 3 l GMC at4 is experiencing loss of power with bucking & stalling. Cylinders are not activating when called check engine light is flashing, it starts rough and makes numerous noises at various speeds, as well as at idle. So I brought my vehicle to my local auto repair shop. Our mechanic found two failed fuel injectors and a failed throttle body. Then the loud knocks in my block failed an acoustic test. He also determined the lifters, push rods and camshaft are experiencing excessive wear. The afm system has failed! he warned me that further use of my motor (with only 42k miles on it) will cause a catastrophic failure. My research shows that these issues are becoming common of 5. 3 GMC motors. We searched the country for a rebuilt motor and found that none are available for the next several months. However, I was able to find a new motor at much greater cost. GMC has declined assistance at this time. My vehicle has no value as is, so I ordered the new gm engine. Without the dod system, these engines were designed to go well over 100,000 miles. I am a faithful GMC owner and none of my previous GMC trucks (2003, 2013, 2015, 2019) had such a major problem. Now the 2020's fuel saving system has failed and requires repairs that amount to half the value of my truck. When a full size truck stalls on the highway it's certainly life threatening.

First my torque converter went out, no warning lights only shaking wehn shifting, I got it replaced already it cost me $2400 second warning light service for brakes, traction and power steering come on and off. And sometimes truck doesn't brake well and steering wheel feels hard to drive, it has happened while on expressway with family. Third engine oil low add oil warning sign comes up alot and I have to add oil, engine has a rough idle now, also when I turn truck on smoke comes out while having a rough idle, recently it started knocking, I haven't moved the truck since than.

Ticking noise coming from engine slight metallic noise as well. Rpms drop and when they drop, you can feel power loss constant hunting in the rpms. Also a weird vibration, not all the time in the front end somewhere.

Coolant control valve and engine cooling fan.

Constant engine issues, cams, lifters. Transmission problems. These engines in these vehicles need to be recalled. I have bought 6 of these trucks and all of them have the same issues. Spending 14k on new engines one after another is ridiculous. These are classified as “work” trucks and can’t handle “working”.

Constant engine issues, cams, lifters. Transmission problems. These engines in these vehicles need to be recalled. I have bought 6 of these trucks and all of them have the same issues. Spending 14k on new engines one after another is ridiculous. These are classified as “work” trucks and can’t handle “working“.

Constant engine issues, cams, lifters. Transmission problems. These engines in these vehicles need to be recalled. I have bought 6 of these trucks and all of them have the same issues. Spending 14k on new engines one after another is ridiculous. These are classified as “work” trucks and can’t handle “working” .

2020 GMC Sierra 1500 elevation 5. 3l engine. Lifter failure due do faulty design I’m afm/dfm systems.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission experienced rough gear shifts. Additionally, the vehicle shuddered while driving. The vehicle was taken to an independent mechanic, who was unable to diagnose the vehicle due to a lack of diagnostic equipment. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 120,000.

I have a 2020 Sierra 1500 6. 2 with 86,000 miles. I have only had this truck 6 months. This was inspected before I purchased with no engine issues. Since purchasing we have driven less than 6000 miles. While driving my vehicle the rod in the engine failed and started knocking. I am a mechanic and I am GMC master certified. Both myself and the owner of the shop I work at diagnosed the vehicle with a bad engine. We looked at the recall for the 6. 2 engine and noticed that many of the 2020 vehicles with this engine have the same issue that is currently being recalled for this specific engine. I called GMC and they won’t fix the issue that the vehicle is having. They won’t perform the recall and again I have only had this vehicle for 6 months and with 86,000 miles should not be having this issue. I am GMC certified and told them that I looked into the recall and they them selves state that some of the defective engines got out into the 2020 models.

I had the rear wheel recall done not long ago and 2 days ago my transmission shuddered.

Transmission valve control malfunctioned, causing rear wheels to temporarily lock, skidding the tires. This almost caused me to loose control, endangering myself and others around me. This is the second time this problem has happened. A recall related to this was addressed on this truck, though it has clearly done nothing to prevent it from happening.

Transmission valve control system malfunctioned, causing rear wheels to lock up at high speeds, in turn causing tires to skid out. This issue almost caused me to loose control of the vehicle, potentially endangering the safety of myself and others near me at the time. This is the second time this has happened while I have been driving this vehicle. There was a recall related to this issue, which was addressed, but very clearly did absolutely nothing to prevent this incident from occurring.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the transmission unexpectedly downshifted. There was no warning light illuminated. The vehicle was able to restart. The vehicle was taken to the dealer, where it was diagnosed and determined that the transmission had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and referred the contact to the NHTSA hotline for assistance. The failure mileage was approximately 70,000.

1. On 05/9/25, the exhaust emissions system malfunctioned, triggering diagnostic trouble code p2c7a (exhaust emissions system failure). This repair, the seventh attempt since June 2024, addressed the same recurring emissions issue previously involving replacements of components such as the nox converter (02/18/25, 03/13/24) and egr valve (02/18/25). The vehicle is available for inspection upon request. 2. The p2c7a failure risks limp mode, reducing vehicle power unexpectedly, which is hazardous on highways, especially while towing. Exhaust emissions system malfunctions release excessive pollutants, posing environmental and health risks to others. 3. Yes, the p2c7a code was confirmed by dealer during the 05/9/25 repair, following prior confirmations (e. G. , 03/31/25–04/05/25. 4. The vehicle was inspected by young Chevrolet-Cadillac during multiple repairs (e. G. , 03/31/25, 05/9/25). 5. Yes, the check engine light and onstar emissions alerts appeared prior to the 05/9/25 repair, first noted ~June 2024 (p2c7a onset). Exhaust smell and reduced fuel economy were observed intermittently. Symptoms persisted post-03/31/25 repair, leading to the 05/23/25 service.

1. Vehicle automatic transmission failed during routine highway driving. Significant drivetrain vibration and limited gear availability. Warning lights included: esc. - electronic stability control tsc - traction system control emergency brake fault light power steering assist reduced flashing yellow engine warning light. 2. White exhaust smoke upon arrival at GMC dealership. GMC technician advised full diagnostic would be required to assess extent of transmission failure and cause of white exhaust smoke. Service technician subsequently communicated that the engine was “failed” and would have to be replaced. Vehicle could not be driven and so full extent of transmission failure could not be assessed until engine is replaced!?!.

Merging onto highway, lost engine power. Cylinder lifter failed, damaged cam shaft, caused damage to coolant system via metal debris, and engine needs to be replaced. 76,000 miles on vehicle, regularly serviced at dealership. I inspected the parts, and was shown the cylinder lifter that had failed and fragmented as well as the galled cam shaft. There were no prior indications of impending failure (no hard shifts, jumping, warning lights, etc). Warning lamps turned on after failure. I asked the mechanic at the GMC dealership what caused the failure, and wasn't given a definitive answer.

The contact owns a 2020 GMC Sierra 1500. The contact stated while driving 65 mph, the vehicle briefly started to shimmy. Upon decelerating, the vehicle returned to normal functionality, but the failure became a regular occurrence. No warning lights were illuminated. The vehicle was taken to the dealer, who diagnosed a failure with the transmission. The contact was informed that the transmission needed to be replaced. The vehicle was not repaired. After investigating the failure, the contact related the failure to NHTSA campaign number: 24v797000 (power train), but the VIN was not included. The manufacturer was notified of the failure, a case was opened, and the contact was referred to the NHTSA hotline for assistance. The failure mileage was unknown.

Engine light came on, performance rough at various speeds / conditions, and smelled like burning and strong urea smell. Gm maintenance identified a failed def injector / replaced.

I am reporting an ongoing safety issue with my 2020 GMC sierra 2. 7l related to the transmission. On two separate occasions within the same month, my truck broke down in the middle of the street, requiring it to be towed to the dealership for service. The first time, the dealer informed me they repaired a part inside the transmission and stated the truck was fixed. However, after picking up the vehicle, the issue persisted, though not as frequently. When I called them, they advised me to drive it for another 100 miles so the valve could fill with oil and the transmission could properly recalibrate. After a few days of driving, the same issue occurred again — the truck stalled in the middle of the street, and I had to have it towed once more to the dealership. This time, the truck remained at the dealer for about a week. They replaced another part inside the transmission and returned the truck to me, noting that it only had about 40 miles of warranty remaining. I asked the dealership to extend the warranty or give me at least two months to test the truck and confirm the issue was resolved, as I am genuinely concerned for my safety and my family’s safety if the vehicle breaks down again on the road. They told me they would respond within two days, but it has now been over 10 days with no response. I am currently afraid to drive the vehicle because of the risk of it breaking down again, especially with my family inside. I am requesting that NHTSA review this issue for potential safety concerns with the transmission system in this vehicle model.

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.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while driving at various speeds, the vehicle jerked abnormally while depressing the accelerator pedal. A dealer was contacted. The vehicle was taken to the dealer, and the technician informed the contact that the failure might be related to the engine or transmission; however, the contact was informed that the vehicle needed to be inspected to determine the cause of the failure. The vehicle was not repaired. The contact stated that the failure had occurred several times. The manufacturer was notified of the failure and informed the contact to file a complaint with the NHTSA hotline. The approximate failure mileage was 41,248.

Vehicle shifting poorly, and I have had a bunch of brake and rotor issues.

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.