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

- Owensboro , KY, USA

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.

- Brighton, MI, USA

Hi I have always taken good care of my 2020 gmc Sierra 1500 at4 6.2 Kept up with its regular and recommended maintenance. I had no warning signs on the dash. So it surprised me that while on my way to work early one morning I was getting off the highway exit and the truck lost power, my steering wheel hardened and it posed a great threat to my life and others on the road, as it suddenly decelerated in a area where people are driving at accelerated speeds. The whole truck was loosing power and shaking hard as I attempted to steer it to a safe location on the side of the road. Had a mechanic inspect it and they determined The truck ended up with a seized engine. I have since not been able to use my truck for 8 months and still currently paying monthly payments of 1000 to pay it off.

- Alamo, TX, USA

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.

- Lawrenceville, NJ, USA

Transmission shurtting, jerks, and vibration, bad torque converter bubble and pelling paint. It feel likes engine is lossing power

- Santa Fe , TX, USA

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.

- Fort Atkinson, WI, USA

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.

- Fort Atkinson, WI, USA

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

- Brighton, MI, USA

Engine light would come on for a few days and than turn itself off. this occurred for about 8/9 months; however, instructed by the GM Maintenance department that if the vehicle came in and the light turned off before they got to it i would be charged for the diagnosis and no work would be performed. Engine light came on and i was able to park the vehicle / they picked it up and read it prior to putting in their lot until a tech became available. GM Maintenance was able to diagnosis that there was an issue with the EGR sensor and NOx catalytic converter without filter failed / both items replaced

- Brighton, MI, USA

Vehicle was going in for warranty recall; however, i requested they look at the DEF system as my DEF gauge would bounce between full and empty; along with, alert me of going into LIMP mode. GM Maintenance updated the recall and noticed that the DEF tank sensor failed and required to be replaced.

- Brighton, MI, USA

Engine light came on and real bad urine smell / burning coming from the vehicle / rough performance. This issue occurred at various speeds / trips / drive types with the only variation being speed from 25MPH to 75MPH. Vehicle went in to discover that the reductant control module software (RCM) out of date, and two NOx sensor failures

- Brighton, MI, USA

Vehicle Stuck in gear. Dealership was delivering the car back to myself when about a mile out from my house when the vehicles made a sudden downshift and was stuck back in gear. Driver called and notified me that it was on its way back to the shop for further work

- Brighton, MI, USA

Vehicle drop in gear / down shift while driving on the highway. went from 75MPH down to 55MPH due to high RPM revs.

- Brighton, MI, USA

This car had lifter motor failure at 135K miles and Transmission failure at 145k miles, the torque converter of this truck is the culprit of many issues as the lifter issues.

- West Covina, CA, USA

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.

- Bristol, IL, USA

Check engine and ECM errors. The dealer replaced one bank lifter. Shortly after, a similar issue was caused by reassembly. Approximate mileage: 30 K. A month later, the same issue, but this time the vehicle was not drivable, with very low engine power. The dealer stated lifter failure and camshaft damage, engine replaced January 2024, mileage 31 K. Currently 42K and had one instance of ECM error, which only lasted a few seconds, but the engine faltered and lost power. At the most recent oil change, the dealer said no error codes were present. GM indicated that my VIN is not covered under the most current recall. Since the engine was replaced in 2024, there is virtually no possibility that the engine replacement was not a new engine and should fall under this most current recall.

- Midlothain, IL, USA

I have taken my vehicle to 3 seperate mechanics (GMC, AAMCO and Independent). They all agree that my valve body inside the transmission must be replaced. The problem is that valve bodies are on a national back order and cannot be fullfilled for months, putting my transmission at risk for further failure. Reading online forums, there are many GMC owners facing this same issue. The mechanics at GMC are requesting that I change out my entire transmission, since that will be a quicker solution than waiting months for that valve body. Now, I am being told that they are having difficulty locating an original manufactured transmission. This puts me in a serious bind because my truck is my only vehicle and there are no valve bodies or transmissions to fix this issue. My truck is only a 2020 and I just surpassed 100k miles. There were no dashboard warning lights that indicated my trucks problem. Only the fact that my truck is shuddering when shifting gears and that a diagnostic tool had to find the source of the problem. This problem started about 5 months ago and has progressivly gotten worse.

- El Paso, TX, USA

The transmission is jerking and sometimes it will not shift enough to get out of others ways. Severe slippage in the transmission I have taken the truck to the shop 3 times for the same issue. Now they tell me I need a new transmission.

- Palestine , TX, USA

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.

- Hockessin , DE, USA

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!?!

- Port St Joe, FL, USA