2020 GMC Yukon

We just purchased our Yukon from a dealership in February (2/7/26) and it was diagnosed with premature failure of at least one AFM valve lifter as it is causing engine misfires, shaking and stalling on 7/30/26. We just hit 67,000 miles on the odometer so we are just beyond the warranty coverage. The lifters were replaced previously by the previous owners on 12/16/24.

The 2020 Yukon started to have serious loss of speed and decelerating issue when the vehicle would slow down and down shift to a lower gear. The issue with this is that once it downshifted it woul not engage in a gear again and leave me stranded on the road. I had to turn off the car and restart it for it to reengage in a gear enough to get it moving again and sometimes I had to try more than once to get it moving once it no longer wanted to engage in a gear. So in the 10 mile drive, I was left stranded at least 15 times. Each time I had to restart and restart again for the vehicle to engage in a lower gear. Once moving, it would sometimes it would engage in a higher gear and sometimes it would not. Thank goodness I wasn't traveling on the highway when this happened. Beware to anyone if this was to happen on the highway while in the middle lane while in traffic. And the check engine light never turned on and thus no code to help detect the issue. Took it the day before to have it looked at and was told nothing was wrong with it since there was a code and they could not duplicate the issue I described. WHAT?? They reset some transmission computer setting but it only made it worse by the next day. Now this 6 yr on 2020 GM Yukon is at the dealership service department requiring a new transmission for $7200. Said that the transmission fluid was showing particles of stuff and color was 'burnt', I think. Transmission fluid was changed at it's regular check up time so that didn't cause the issue and nor should it have bits and pieces in it and discolored. Is there any recourse to GM and it's crappy transmissions??

TRANSMISSIONS ISSUES. Not transitioning/ shifting into gears smoothly or at all. When it does transition/shift it is rough and harsh. When my car transitions to a lower gear then it will not transition back up to a higher gear causing my vehicle to drop speed significantly that I am a safety hazard on the road. Example: when it shifts to a gear high enough that the vehicle can reach 40 mph and there is a need to decelerate it does but once it drop to lower gears it cannot engage again to a higher gear leaving me stuck going at most 10 mph with not opportunity to excelerate in traffic to a higher speed. The transmission control module (TCM) software was updated with no improvement.

I purchased my 2020 Yukon Denali on July 8, 2024 from Classic Buick GMC in Painesville, Ohio. The check engine light started going on and off a few months after purchasing the vehicle. When I called a mechanic he stated that I should wait until the light is on and then bring in the vehicle. In early May 2025, I took my vehicle to Mike’s Automotive in Middlefield, Ohio after the check engine light began coming on during extended drives (approximately five hours or more). The shop ran a diagnostic scan and advised that the oil pump needed to be replaced. Seeking another opinion, on May 14, 2025, I brought my vehicle to Classic Buick GMC Service, the dealership where I purchased my GMC Yukon. After diagnosing the vehicle, they advised that the check engine light was related to an Engine Oil Pressure Control Solenoid stuck in the off position (P06DD). This fix would cost $3,584. This fix would require the oil pump to be replaced as indicated by the previous repair shop. On May 29, 2025, I took the vehicle to Avenue Auto Clinic in Painesville, OH, where the oil pressure valve and sensors were replaced. The mechanic also advised that I change the oil every 3,000 miles, use OEM oil filters, and thicker oil. He also advised me to check the oil every 1,000 oil and add as needed. I do have to add oil approximately every 1,500 miles and I change the oil every 3,000 miles. I am concerned that my vehicle has the same engine-related defect as the Yukon engines currently under recall. Multiple mechanics have informed me that my vehicle is equipped with the same engine as those affected by the recall. I am requesting that my vehicle be added to the recall. Yes, my vehicle is available for inspection.

I purchased a new 2020 GMC Yukon in May of 2020. Between May 2020 and November 2025 the vehicle was routinely serviced on or before the due date recommend by the manufacturer. I had not experienced issues with the vehicle until November 2020 when the check engine light abruptly appeared and the vehicle began driving very rough. I immediately took the vehicle to the local mechanic who identified two codes (P0300 and P050D) related to the engine issues. The vehicle was towed to the dealership due to the fact that I was instructed it was unsafe to drive long distances without additional diagnostics. The dealership disassembled the engine and found coolant leaking into cylinder six. There were no cracks or otherwise clear means of entry for the coolant into the engine. The dealership instructed us that we would need a complete engine replacement. Upon further research of this issue, it was uncovered that a Service Bulletin had been issued for this very issue. The reference number is 20-NA-166, updated March 2024.

We purchased the vehicle used in April 2025 with 79,851 miles. All service records were documented via Carfax. Vehicle was in impeccable condition. We drove it for approx. 8,000 miles until July 10, 2025, when a loud knocking sound started coming from the engine - approx. mileage 87,600. We drove the vehicle home 350 miles. The knocking sound continued and got slightly worse. We drove it to the nearest dealer (30 miles) and the mechanic said it sounded like a camshaft problem. However, they could not get it in for over 60 days. We drove to another dealer (45 miles). The mechanic said he thought the entire engine was bad. We left the vehicle there and about a week later they were able to confirm that it was TOTAL BEARING FAILURE. Mileage 88,054. We were told that a new engine was needed as well as a radiator and new oil lines, etc. Total estimate $18,000. They also said there was no timeline they could guarantee because of the current GM recall. Of particular note and concern...at no time did the 'check engine' light come on or any other warning system activate. Both mechanics were genuinely perplexed at this. The repairs were ordered and the vehicle is now repaired. However, GM has not confirmed a cost share for the repair billing and we are now almost 60 days since they received the paperwork from the dealer so we still do not have our vehicle back. We filed a complaint with GM and a case number was assigned so they are fully aware of the issue as is the dealer who did the repair.