general problems of the 2021 GMC Sierra 1500 - part 1

While driving, the vehicle experienced a sudden and momentary loss of power, similar to briefly applying the brakes, after which power resumed. This was followed by a progressively louder squealing noise. I pulled over to investigate, at which point the engine shut off and a low oil pressure warning appeared on the dashboard. The vehicle would not restart. The vehicle was then towed to a dealership, where initial inspection suggested the issue may be related to the l87 recall involving the crankshaft bearing.

My vehicle began exhibiting symptoms consistent with a failed engine coolant flow control valve. The check engine light illuminated, and diagnostic testing indicated a fault related to the coolant control valve system. In addition, I experienced abnormal cooling system operation, including the engine cooling fans continuing to run after the vehicle was shut off. Vehicle was tested few times in auto zone these symptoms affected the normal operation of the vehicle and are consistent with the condition described in special coverage n252508341. Based on the diagnostic findings and vehicle symptoms, I believe my vehicle qualifies for coverage under this program. I respectfully request that my vehicle be inspected and evaluated under special coverage n252508341 and that any eligible repairs be performed according to the terms of the coverage program.

The contact owns a 2021 GMC sierra. The contact stated that while driving at approximately 40-45, the engine warning light illuminated. There was an abnormal sound coming from the fan. The vehicle was taken to the local dealer, where it was diagnosed and determined that the coolant flow valve needed to be replaced. The vehicle was not included in a special coverage program. The vehicle was not repaired. The manufacturer was not contacted. The failure mileage was approximately 50,000.

While driving my vehicle, the engine and transmission lost power and the check engine light came on. The vehicle went into limp mode and engine propulsion was limited. Had I been traveling at a faster speed, this would have been very unsafe. After coming to a stop, placing the transmission in reverse did not move the vehicle and there was a grinding noise. I was able to savely move forward in limp mode, but the shifting was harsh. I was able to find an empty parking lot to safely park. The truck was towed to jim winter dealership in jackson mi for inspection.

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving at an undisclosed speed, the reduced power mode and check engine warning lights illuminated. The vehicle was taken to the dealer, where it was diagnosed with coolant control valve failure. The contact was informed that the coolant control valve needed to be replaced. The vehicle was not repaired. The contact was informed that the failure was like the failure description in special coverage bulletin: n252508341. The manufacturer was made aware of the failure but provided no assistance. The contact was informed that the VIN was not associated with the special coverage. The failure mileage was approximately 58,500.

While coasting down or under very light acceleration between 12-20 mph the vehicle has a shudder like driving over a highway rumble strip. While cruising on the highway at 65+ mph, the vehicle has a light shudder or vibration. Vehicle has been checked numerous times for wheel and tire inconsistencies. Brake pads and rotors have also been replaced with no change in issue. Headlights daytime running light changes color from bright white to purple during warm weather. The vehicle has been to 3 different gm dealerships and they acknowledge the issues but do not provide a resolve.

My truck went into reduced power mode while driving on the highway (very dangerous and life threatening) for a coolant control valve failure code (p1098), which has been confirmed by a gm dealership. Gm already has extended the warranty for special coverage n252508341 for selective VIN numbers only and my VIN number is being excluded which isnt safe at all or fair. My truck is a 2021 sierra denali 3. 0l lm2 duramax and has the same exact problem (coolant control valve failure code), and the same exact faulty part, and the same exact motor (lm2) which directly matches the perimeters for the n252508341 special coverage program but my truck isnt being recalled or covered for repair due to them selectively choosing certain VIN numbers to recall only.

2021 GMC sierra after purchase at 4,700 miles had issue with the lifter rods and were replaced at that time. Now the truck has a little over 67,000 miles and once again have the same issue. This appears to be a known issue with this truck and the 5. 3l engines. The truck is in repair and since it is slightly over its warranty of 60,000 miles. The dealer will not cover the repair. Seeing that this is an ongoing and known issues with service bulletins it seems that this should be a potential recall. We were lucky that we identified the issue early and were able to get to the dealer to fix. Otherwise we could have broken down in the middle of our daily commute in the expressway.

The truck randomly will not detect that it was shifted into park. Shifting between gears and back to park does not automatically fix the the issue and has taken up to 10 mins to turn the truck off. The adaptive cruise controls stopped working and can still use regular cruise control. Just not adaptive. It appears greyed out. The truck has thrown the error code: p1098, engine coolant control valve position sensor minimum stop performance. The truck would go into limp mode until the error was cleared. This error has appeared 4 times over the past five months. The most recent date of it happening was today. 06/30/2026.

Catastrophic engine failure the connecting rod went through the block. It is my understanding that defective components: manufacturing defects in the connecting rods and crankshafts can reduce oil film strength, leading to severe wear, metal debris, and catastrophic engine could be the proiblem.

Coolant control valve.

Engine coolant control valve position sensor minimum stop performance, and chevy recalled this on this same motor and GMC needs to pays for this as it’s a major problem!.

Coolant control valve not working correctly exhaust fan on high all the time but is never overheating this has been going on for a week it shows there is a 150000 mile warranty on it but not for mine.

I have the same model and year for GMC as bulletin 25na-185, engine coolant control valve failures on 3. 0l duramax (Dec 4, 2025), and am experiencing the same exact issue. Apparently my VIN is not included and I can't get an answer from GMC or the local dealer why it's not covered or how to have it reviewed to be added.

Engine coolant control valve needed to be replaced. Special coverage (n252508341) was issued out by gm to fix this problem on 2021 GMC Sierra 1500 vehicles.

2021 GMC sierra at4, VIN [xxx] , NHTSA campaign 25v-274, gm case xxx. Brake pad monitor failed at 128,923 miles -- 24 miles after leaving penske Chevrolet (released at 128,899, ro xxx, 04/17/2026). Brakes became spongy immediately following service. Monitor disabled entirely to stop recurring red service system alert. Root cause is a burnt fuse block ground fault confirmed in writing by two gm-authorized dealers. Ray skillman (ro xxx, 06/05/2025) documented the fault then deleted labor operation 14buz engine electrical from the recall repair work order. Penske documented verbatim: "all of these other faults share this same ground circuit. " the recall repair at ray skillman used a remanufactured short block instead of a complete engine per n252494002. The original seized-engine oil pan has never been replaced across three dealerships and 128,000 miles. Gm's own part 573 filing states this defect "increases the risk of a crash. " I drove 300 miles on an interstate on 04/22/2026 with active brake warning and no loaner because gm executive resolution refused to authorize one. Three gm dealers have inspected this vehicle. Gm executive resolution team [xxx] ) has not returned calls or emails and has not confirmed in writing this vehicle is safe to operate. Onstar issued a critical alert for p0617 on 04/15/2026. Zero brake faults existed in the 13 months prior to the penske visit. This is a direct continuation of unresolved electrical damage from a botched federal safety recall repair at 384 days and counting. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

Coolant control valve failing. Warranty not covering this part. Seems to be a manufactured issue. Happening on a lot of 2021 gmnc sierras with the 3. 0l duramax.

My l87 engine has failed due to a manufacturing issue. The recall number for this issue is n252494000. Upon contacting GMC, they state that my VIN number is not included in this recall despite having the same exact issues. I took the vehicle into a mechanic as soon as a problem had arose.

While driving into work, I noticed a knocking sound from the outside of the vehicle. Once parked, upon further inspection I narrowed down the area of the noise to the bottom rear of the engine/front of transmission. Fortunately, I was able to park in front of my office building and wasn’t stranded on the side of the road but under different circumstances it could've been the side of a busy highway or hours from home. I had the vehicle towed to the dealership I originally purchased from, the dealership was able to duplicate the issue with me present. Later that afternoon I was informed that the engine had failed and a replacement would be ordered. There was no prior indication of a problem or warning/cel’s. The engine failed after the dealership had completed the engine recall ( pico test and 0-40w oil change ) related to the vehicle. I am reporting this in hopes that it helps with the investigation. This has been very disappointing for me as I have supported the brand of vehicle for many years. Only to have many issues under 80,000 miles and to lose confidence in the vehicle I purchased and the company.

Driving normal traffic . Started hearing ticking . Check engine light flashing ,service esc and braking system light up. Parking not loud ticking from engine bay.

The afm caused piston flapping and other major engine problems such as abnormal wear. The problem with the engine could have caused a catastrophic failure along the side of a highway. The problem has been diagnosed and the engine has been replaced at my expense. The repairs were made at a local mechanic shop. The engine would start make a loud ticking noise at 2000 rpm or above. The mechanic shop referred to this as piston flapping. This was caused by inadequate oil pressure at all cylinders due to the active fuel management.

Engine has a terrible shake, and I was informed by a mechanic that it has a misfire and no compression in piston number seven.

The engine completely shuts off when I stop at a stop sign or stop light. I have been stuck in traffic intersections on several occasions unable to move when the light turns green. Eventually this will lead to me getting rear ended and pushed into in the middle of an intersection. My life is in danger when I drive this vehicle. I got my engine replaced and still the same issue is occurring with the auto stop and start system.

There is a recall on the 6. 2 motor that is in my truck at my last oil change they performed a pico scoop diagnostic on the truck said it passed and gave it the new type of oil and oil cap that was suppose to fix it. Now a couple months later I walk out start my truck to let it warm up and after starting all of a sudden the engine started nocking bad and loss of oil pressure and on dip stick. I looked it up and this is what happens when the engine fails due to the massive recall on the 6. 2 engines. I called the dealer and they are having me tow the truck potentially at my expense for them to look at and decide if it falls into the category of the recall after they did the test, and at one point told me that cause they did the test it is no longer recalled. I am being told people who have had the engines replaced because of the recall that the replacement engines have failed as well. I have a 9 month old baby and this left me stranded and unable to pick him up from daycare I had to scramble to find somone able to do so. I'm concerned that this could have happened while driving and having him with me or being left stranded somewhere. I'm glad it didn't happen when I was dropping him off that morning and while I was driving and meanwhile while they look at the issue and decide weather this falls under there recall or not and while it gets repaired I'm left without a vehicle and to be honest I don't feel safe even if they do repair it as there seems to not be an actual fix to the situation. This is unsafe and unacceptable for the price we have to pay for these rigs and the safety regulations and standards we have, how is this even an issue.

L87 engine failure 4 months after it passed the recall test. Experienced shuddering and rpm fluctuation with the cruise control set. Was thinking torque converter. Got it replaced under warranty and the the issues were still there. A week after new tc the truck was running very rough driving down the road. Check engine light along with a low oil pressure warning and lost all engine power going 60mph. Would not re fire. Had to coast to a stop with no headlights on only fog lights. Truck is at dealership now will be needing a new engine. P0016 engine code. The truck was in the shop multiple times for misfire and rpm’s jumping and cruise control turning off on its own.

-the engine in my 2021 GMC denali 1500 with the 6. 2l engine failed its second engine with ~4,000 miles on the new engine. It is currently at GMC dealer waiting for a 3rd new engine. - fortunately I was parked when the failure happened and the engine locked up. -dealer confirmed that a valve dropped and damaged the cylinder wall. - there were no warning lamps or other indication that a failure was about to happen. -current mileage ~91,000. First motor changed ~85,000 due to recall with previous owner.

I am filing a complaint regarding a catastrophic engine failure in my 2021 GMC Sierra 1500 equipped with the 6. 2l v8 engine. While driving under normal conditions, the engine suddenly failed without warning and threw a connecting rod, rendering the vehicle inoperable. There were no prior warning signs such as knocking, overheating, oil pressure issues or even a check engine light. The vehicle has been properly maintained, including regular oil changes using manufacturer-recommended 0w-40 oil. This failure created a serious safety concern due to the sudden loss of power while driving, which could have resulted in a dangerous situation, especially at highway speeds or in traffic. I am aware that general motors has issued a recall and/or is aware of similar failures involving the 6. 2l engine in certain 2021 vehicles. However, my vehicle’s build date falls just outside the currently defined recall range, despite experiencing the exact same type of catastrophic failure described in those cases. My build date is 12/20 and the recall was issued for 3/21. Given the similarity of this failure to known issues, I believe this defect extends beyond the currently identified recall population. This raises concerns that additional vehicles, including mine, are at risk of sudden engine failure without warning. I am requesting that national highway traffic safety administration investigate this issue further and consider expanding the recall to include additional affected vehicles outside the current build date range.

Loss of power, and knocking from the engine while driving. Check brake system, check srs, check parking brake and check engine light flashing came on at the same time. The problem has been reproduced at a mechanics shop and has been determined that cylinder 6 is dead.

While driving at normal highway speeds, I got a warning light for engine overheat condition and cooling fans came on. I also got a warning that the engine would go to reduced power. I reported this issue to my local GMC dealer. Was told that this was a comm problem with this engine however: my VIN number indicated that this vehicle was not covered under warranty n252508341. I was advised to bring it in for a $250 diagnostic check and repairs could not be made for at least 2 months because of backlog. Took my truck to a local vehicle repair shop where they diagnosed a faulty coolant control valve and replaced it for me for $2388. 43. Why did GMC desert me?.

Took it to dealer for engine sound said nothing was wrong 4 days later rod bearing went out while driving. Truck no longer able to drive.

Engine developed a low knock type noise just above idle while beginning to move in the parking lot. It was also noted pulling away from an intersection at low rpm under light acceleration. Oil pressure was normal, 30 psi and approximately 50-60 at cruising speed. Low level knock began earlier in the day but no other symptoms. Oil level was checked and found to be at proper level. At mile 2 into my trip a chirping/ squeak type noise was heard under light throttle and light load at approximately 1500 rpm. The noise stopped when accelerator was released. Rough running sensation followed the noise under the load. Noise returned when the accelerator was pressed and then the engine stopped running while traveling 45-50 mph. Placed the shifter to neutral and attempted to restart, engine rolled slowly for a brief moment and then locked up entirely. Starter only clicks when attempted after that. Vehicle left me stranded with no heat on the shoulder of the highway in the dark in northern michigan on March 5, ambient temp was 28 degrees. Vehicle towed to closest dealership which is also where it was purchased for inspection on 3/6/2026. General motors customer care contacted and case opened. No assistance with repair at time of callback.

6. 2 lifter failure at 44500 miles.

The contact owns a 2021 GMC Sierra 1500. The contact stated that while operating the vehicle, the check engine warning light illuminated and remained illuminated. While driving at various speeds, the vehicle entered limp mode, causing the vehicle to decelerate. Additionally, the radiator fan was continually activated while operating the vehicle. The vehicle was taken to the local dealer, who diagnosed that the coolant control valve was inoperative and needed to be replaced. The vehicle was not yet repaired. The manufacturer was notified of the failure, but no assistance was offered. The failure mileage was 119,000.

Began with a misfire on cylinder 5 code p0305. Replaced spark plugs, wires, and coil pack. Misfire still existed. Fuel injector on cylinder 5 was stuck open and had to be replaced. Misfire still existed. No spark from new coil pack on cylinder 5, replaced coil pack connector. Misfire still existed, but lifter tick became present. Removed cylinder head and found exhaust lifter on cylinder 5 was bad and needed replaced. Currently awaiting parts delivery (only available through gm dealer). Have been without vehicle for 7 weeks now. Was told this was most likely related to active fuel management.

I was driving on a highway on my way home from work. Thank god there was not a lot of traffic because my truck just shut off lost all power, then I received a message on the dash to put on neutral and restart. I tried multiple times to turn it back on. It never turned on and had to get it towed to nearest dealership. It took them a week to inform that the engine locked up even though I tried to take it for the recall they told me to wait and reschedule the appointment. Never got a new appointment until the engine failed and I got it towed to the dealership and have also not received a new kind of loaner from gm. This will be my last GMC truck I purchase.