general problems of the 2021 GMC Sierra 1500 - part 2

Transmission valvebody failure, causing rapid, repeated rear wheel lock ups. Videos can be provided. These happen almost daily at highway speeds. This will cause a very bad accident.

The valve body failed, brought it in to a GMC dealership 3 months ago they told me the valve body is on back order. Last week they received the new valve body installed it and tried to program it. While programming it, the brand new valve body failed. So now I am stuck again with no eta of when a new valve body will be sent to the dealership to fix the issue. This is obviously an issue with the make and model and in my opinion should be a recall. I do not feel safe if I ever get my truck back from this issue due to ongoing valve body failures nation wide and two on my end.

Vehicle began to slip or shift hard when putting it in gear or coming to a stop. The next morning the vehicle would not move when put in drive or reverse.

My wife was driving at highway speeds with all are kids when the trucks motor suddenly loss all power all check engine lights illuminated and what I'm assuming had major engine failure causing rod knock.

On 10/21/2025 as I was traveling on the highway in kansas at 60 mph, the vehicle lost power and the engine went into limp mode immediately reducing the speed dramatically. Multiple warning lights flashed on the screen. I was able to get the truck to the side of the highway. The vehicle never started again. I was informed by the dealer that the vehicle would need a new engine.

I just took my 2021 GMC sierra 1503. 0 duramax diesel into faulkner Nissan, today 10/18/2025 m, to have that recall fixed. I picked it up from the dealership and drove about 10 miles before it went into limp mode and reduced power mode while I was driving and started to shift very roughly and I’ve never had any issue like this before they supposedly fix this recall, I think the software patch made it worse in my case. Now my vehicle is throwing a bunch of different transmission error codes, that it has never produced , and it is going into reduced power mode,as I’m driving and going into limp mode as I’m driving, which you never has done before and it feels like it’s stuttering in early gears now and the idle was really rough it didn’t idle at a specific spot it went from 800 to 1300 back down to 800 when it should’ve just been idle at 800. I don’t know what to do. It seems like this recall made the problem worse for me and my truck in this case, I don’t know what to do and I don’t know where to go. I hope you guys can help us. Please make GMC take responsibility before somebody gets killed. If they haven’t already this issue is extremely dangerous and I’m sure is destroying the transmission. I don’t feel comfortable driving my family in my vehicle anymore because of this issue it is terrifying….

2021 harley davidson sierra 4wd, 6. 2l l87. Started the truck in the morning and immediately heard intermittent, very loud banging noise coming from engine. Shut truck down quickly and had it towed to dealer. Diagnosis was bent pushrods & failed lifters which were replaced under warranty. Factory warranty expired only 4 months after this failure, and the recall does not include my VIN so I did not get an extended warranty or any other protection. Gm has yet to even reimburse the tow bill. Completely unacceptable for a truck that was well over $100k when new.

Dtc code p1098 present related to faulty coolant control valve on 3. 0 duramax diesel engiine. This is a known issue with this engine and is supposed to be covered under the 100k mile powertrain warranty. Previously took vehicle into dealership for repair involving replacement of the coolant control valve but was told reprogramming of the ecm was required first step per gm repair bulletin. Reprogramming cost me $195 and was told this was not covered under the 100k powertrain warranty. Now, a few months later, the same issue and dtc code p1098 happened again while driving on freeway at freeway speeds and caused vehicle computer to limit speed of the vehicle which caused hazardous situation in construction zone as was not able to maintain speed of traffic while towing trailer with boat. I also understand that gm has issued special extended warranty related to this coolant control valve in September 2025 which extends the warranty coverage up to 15 years and/or up to 150k miles but I was told at the dealership that my VIN# does not qualify for this extended coverage for some unknown reason?.

Transmission on my vehicle has failed three times since I bought the vehicle in October of 2021. Vehicle currently has 39,000 miles. First transmission issue was resolved by the dealership by replacing the transmission valve body. This solved the problem for approximately 12,000 miles. In September of 2025 with 39,000 miles the transmission suffered a catastrophic breakdown which lead to complete transmission replacement. After being “fix” the vehicle suffered another catastrophic transmission failure within 400 miles of the complete transmission replacement. This incident caused the vehicle to shut completely down and I was stuck in the traffic lane of the us highway. Fortunately my vehicle and I were not struck while waiting 30 minutes for a tow truck. Presently the vehicle is back at the dealership awaiting repair. From my review of available on-line information it appears there are 10’’s of thousands of GMC sierra pickups with major transmission issues. This needed to be addressed before someone is killed due to the poor quality of these GMC trucks.

I have a 2021 GMC Sierra 1500 at4 3. 0l diesel pickup truck with 98,500 miles. The coolant control valve failed on my vehicle and for some reason it is not covered under gm's special bulletin that covers this part 15yr/150,000. Ridiculous.

For close to one year, there feels like a catch, grind, stall, or slight shake, mostly while the vehicle is shifting gears, made worse or noticed more by higher speeds like driving on the highway vs. Slow city streets. It's difficult to explain or assess so not sure if it is the engine or transmission. With the open recall from GMC on some vehicles with the same engine as mine it is concerning that maybe it should have been included.

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” .

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 45-50 mph, the engine revved and the transmission unintendedly downshifted, causing the vehicle to decelerate unexpectedly. The transmission then seized, and the vehicle skidded. No warning light was illuminated. The vehicle was towed to the dealer, who determined that the transmission had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 127,000.

Transmission failure at a little over 120,000 miles while towing a side by side on the highway. This highway has a speed limit of 80 which is dangerous when the vehicle stops working properly for myself and any other drivers in itself. Earlier this year the transmission had been updated due to a recall and was deemed to work good by the dealership but didn’t notice any difference. Had an engine light pop up a couple hours before but no messages or any other signs to inform me of the issue and was still working fine with no struggle until it gave out.

I was driving at highway speeds probably doing 55 and another vehicle pulled out in front of me forcing me to slow down rapidly. That’s when my wheels locked up and my vehicles wheels locked up in the middle of the highway. Screeching tires, almost like the vehicle went into park for a second. After about two seconds, I was able to continue driving a highway speed no check engine lights no error codes. It felt like I just hit something nearly gave me a heart attack. My family was in the car. It felt like we all almost died. It was terrifying. This transmission issue recall situation has happened to me more times than I can count. Now it’s almost a guarantee that if you have to shift too hard too fast it locks up the differential and it is terrifying. Every time.

I own a 2021 GMC Sierra 1500 equipped with the 6. 2l l87 v8 engine and 10-speed transmission. The vehicle exhibits the following issues: persistent lifter ticking noise audible from the driver-side wheel well, even when the engine is warm. Rough idle that is noticeable at stops and low-speed conditions. Transmission shifting problems, specifically harsh or delayed shifts when downshifting from 3rd to 2nd gear during deceleration. These symptoms raise concerns about potential lifter failure and transmission defects. I am aware of gm’s recall (25v-274) and NHTSA engineering analysis ea25007, but my vehicle’s build date (January 2021) currently falls outside the official recall window. Given the similarity of symptoms to those under investigation, I believe my vehicle may be affected by the same defect. Safety concern: the rough idle and shifting hesitation could lead to unexpected loss of power or unsafe driving conditions, especially during deceleration or merging. Request: please include this complaint in ea25007 and consider expanding the recall to cover earlier builds. I am willing to provide service records, videos, and additional documentation upon request.

I have contacted local GMC repair facility (frank brown in lubbock TX. ) about the safety recall on my 6. 2 liter engine to attempt to schedule an inspection of my engine and cannot get them to inspect the engine which the recall notice said they would do. They continue to stall and say the inspection isn't approved by gm. I've tried 3 different times to address this isuue without satisfactory results. I recieved the gm safety recall n252494000 notice for my vehicle in may 2025.

Engine coolant control valve failure. This is a widespread issue on 2020-2022 3. 0l diesel trucks and it hasn’t been addressed by gm, leaving owners to pay out of pocket for a faulty part.

The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving 15 mph, the vehicle briefly jerked and jolted, prompting him to discontinue driving the vehicle. The vehicle returned to normal functionality, but the failure became a regular occurrence. The check engine warning light was illuminated. The vehicle was taken to the dealer, who diagnosed failures with the output shaft speed sensor and the transmission control module. The vehicle was not repaired. The manufacturer was notified of the failure but provided no assistance. The failure mileage was 89,000.

The contact owns a 2021 GMC Sierra 1500. The contact received notification of NHTSA campaign number: 24v797000 (power train) and the dealer performed an interim repair on the vehicle. In March 2025 the part was available, and the recall repair was completed. The contact stated that on one occasion while driving at an undisclosed speed and then coming to a complete stop, the vehicle jerked and the transmission unexpectedly downshifted. The message “low power mode” was displayed on the instrument panel. The vehicle then failed to accelerate as intended while depressing the accelerator pedal. The contact drove to a parking lot and turned off the vehicle. The vehicle was towed to don moore Chevrolet GMC, where it was diagnosed with transmission control valve failure. The contact was informed it would be months before the repair could be performed. The vehicle was towed to another dealer, where the transmission control valve failure was confirmed, and the contact was informed there were metal shavings found inside the transmission. The vehicle remained at the dealer unrepaired. The manufacturer was made aware of the failure. The failure mileage was approximately 115,000.

Torque converter failure confirmed by dealer: was driving at high way speeds when I noticed a slipping sensation from the transmission upon any sort of acceleration. No warning lights were illuminated or any symptoms leading up to the failure. This could have potentially caused me to lose any form of acceleration that would enable me to get off of the highway or away from a situation requiring sudden acceleration.

What component or system failed or malfunctioned, and is it available for inspection upon request? the coolant control valve has stopped working. How was your safety or the safety of others put at risk? while driving the truck can overheat very quickly which can lead to dangerous temperatures as well as cause me to make an emergency stop on the highway to allow the truck to cool down. Has the problem been reproduced or confirmed by a dealer or independent service center? yes, I have discussed with a dealership in person and independent mechanic who have confirmed the issue and confirmed it is a very common issue. So common that the only replacement part for the problem is backordered. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? no, they confirmed the issue without inspecting the vehicle because of how common it happens. Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? there were no warnings before the issue. The issue happened and then the check engine light turned on as well as a "reduced engine power" message.

I own a 2021 GMC denali with a 6. 2l v8 l87 engine and 45,500 miles. I have confirmed the presence of metal shavings in the oil and oil filter, indicating that the engine is beginning to fail. When I took the vehicle to my local dealership, I was informed that there is currently no fix for this issue and was advised to continue driving the vehicle. This poses a serious safety risk—not just to me and my family but also to others on the road. A sudden loss of power could lead to a dangerous accident, and I do not want to be responsible for something preventable that could harm innocent people. My concern is that gm is aware of this engine issue but has instructed me to keep driving the vehicle, despite the known defect. How can gm be allowed to avoid accountability for such a critical safety matter? if a fatal accident were to occur, would the responsibility fall on gm or the NHTSA for failing to act? it’s also troubling that gm continues to profit by selling new vehicles, including the 2025 models, with similar issues, all while neglecting to provide solutions for affected customers like me. I purchased this $80,000 truck in good faith, but now no dealer wants to trade or buy these trucks without me taking a significant financial loss—something gm should be responsible for. As a taxpayer, I find it unacceptable that we bailed out gm in the mid-2000s, yet they continue to disregard accountability for their actions. I urge the NHTSA to take this issue seriously. A specific deadline should be set for gm to resolve this issue, and they should face daily penalties for every day they fail to provide a fix. If no resolution is possible, full refunds should be mandated. Please address this issue promptly, as it affects real people’s safety and financial well-being every day.

I was driving on the freeway and my GMC sierra at4 received a notification that I could could no longer accelerate. I pulled off to the side as safely as I could in a slanted hill in a major freeway with no shoulder. I sat on the side of the road for 45 min and then ran out of diesel gas waiting for the tow truck. We took into GMC and they said nothing was wrong, we were out of gas. But I ran out of gas waiting for the tow truck. The truck never shut off and ac still going, I just couldn’t accelerate. We’ve had the truck in the shop every single month for the past year for sensor issues and replacements and have all the documentation of the last few years of similar issues. No extensions of warranty’s nothing. Well we started to smell something burning this week and now we were told today we have a faulty fuel pump that will cost us $1,000 to fix and is not covered under our warranty. The truck is still under warranty, so why is something in relation to the power train not covered? there is a current t recall on other GMC models of this year for this fuel pump issue and the safety recall is exactly what happened to us on the freeway and the issue we have now. Why has this not been extended to other Gmcs????? my entire family could have died on the side of the freeway!!.

Wn a 2021 GMC Sierra 1500 6. 2l (VIN: [xxx] ), which is now experiencing a severe misfire, engine ticking, and diagnostic code p318a. I’ve confirmed this issue is related to gm recall n252494001 for engine connecting rod/crankshaft failure. However, I’ve been told my VIN has not yet been activated for recall repairs, and both the local dealership and GMC support have refused to escalate my case or offer assistance. This is a known safety issue, and I’m now at risk of total engine failure and significant financial loss while waiting for gm to act. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

This vehicle experienced catastrophic engine failure while I was on vacation 400 miles from home. I have researched this failure and there is a class action lawsuit against GMC. My truck has been at the dealer for 25 days and still waiting for authorization from fidelity warranty services. Considering it’s such a common problem I feel GMC should be paying for this. At the very least the warranty company is aware of this problem and purposely delaying the authorization to repair. I just bought a new camper which I cannot use. I am fisherman and cannot use my boat. My beach pass is also on the vehicle. So essentially my summer has been ruined by a company that produced a faulty vehicle and didn’t discord this information to me.

The check engine light came on at one point. I took it to figure out why the check engine light was coming on and the scanner indicated that the nox catalyst was below threshold. I researched it and it is a common issue. The check engine light eventually turned off after a couple of days. About 2 weeks later it came back on. I noticed as I was driving the coolant fans were running at 100% meaning that they were blowing long and hard. So I scanned it and it said that the engine coolant valve was at fault. This is also a common issue with the vehicle, particularly in the 2021 GMC Sierra 1500 3. 0 turbo diesel. It is a faulty part and it costs thousands of dollars to replace. How can these two issues not be on a national recall by gm? they are too common and very expensive to repair. This issue is so common that now the valve is on a national back order. Meaning the parts may not be available for 30-120 days. The vehicle is not safe to drive with a bad engine coolant valve. I have now a rental car for the past 7 days while my truck sits waiting for a valve to arrive and pay thousands in repair just to drive it again.

What component or system failed or malfunctioned, and is it available for inspection upon request? the valvetrain system failed due to broken rocker arms, which resulted in additional internal engine damage. This failure occurred under normal driving conditions. The affected components have not yet been discarded and are available for inspection upon request. How was your safety or the safety of others put at risk? the failure caused sudden engine misfiring and knocking, reducing engine power while I was operating the vehicle. This significantly compromised acceleration and response time, especially during merging and lane changes, which could have led to an accident. Any unexpected loss of power or engine instability at highway speeds poses a serious risk to myself, passengers, and other motorists. Has the problem been reproduced or confirmed by a dealer or independent service center? yes. The issue has been diagnosed and confirmed by an independent certified mechanic, who verified the broken rocker arms and resulting engine damage during inspection. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives, or others? the vehicle has not yet been inspected by the manufacturer, police, or insurance representatives. Only a certified independent mechanic has inspected the failure thus far. Were there any warning lamps, messages, or other symptoms of the problem prior to the failure, and when did they first appear? yes. The check engine light appeared and the engine began running rough and producing a knocking sound. These symptoms occurred just prior to the confirmed failure and prompted me to stop driving the vehicle immediately and have it inspected. Given the seriousness of this issue and reports from other GMC 5. 3l engine owners experiencing similar rocker arm failures, I urge the NHTSA to investigate this potential defect. It poses a real and significant safety risk.

The coolant control valve is faulty and is on national backorder causing months of my truck sitting in the shop. This is not an isolated issue. Gm is claiming it is not covered under warranty, but the part design is clearly a serious issue.

Have owned my 2021 GMC Sierra 1500 with the 3. 0 duramax for a year and the check engine light has come on multiple times for a "coolant control valve" issue. The truck runs the fans at 100% and puts the truck into reduced power at least once a day. I have read that gm sometimes will not cover this repair under powertrain warranty even though it's an engine problem. Please fix this issue! to answer the previous questions, the coolant control valve is malfunctioning, and the truck is currently at the dealer being inspected. Yes the dealer has said this issue is common on these trucks (confirmed by national GMC in american fork, utah). Yes the check engine light has appeared multiple times. These issues started appearing in June 2025.

Right after I bought the car I had a very bad misfire on cylinder 1, the car would shake at idle. Took to dealership and they said they replaced all the spark plugs and replaced cylinder 1 coil. About a week later the misfire and shaking started again but this time it would come and go. The check engine light would be on then it would go away for a bit and then come back on over and over again. The only thing that seemed to work is if I disabled the stop and go start system and put the car in l9 to disable the afm. This seems to work and I have since bought a disabler for these systems. However, there is still a vibration at idle and I feel that its a temporary fix to a bigger issue. This is my daily driver and constantly have my children in the car and just want the car to be safe for everyone. The transmission downshifts rough and at times seems to slip/lock up while driving. I haven't brought it to the dealership for this as of yet.

Received my truck back after replacement of the front transmission pump and idle gear, the same day the transmission had horrible down shifts, sometimes it would just downshift into neutral and bounce off the rev limiter. The service advisor told me that my transmission had to "relearn" my driving habits when I called him and would take 200-400 miles. . I drove it one more day and drove it back to the dealer to have them drive it. The agreed that something was wrong, but didn't know what and had to contact gm engineers. 2 days later they told me that the valve body needs to be replaced. I dropped it off to find out that it had been ordered with zero eta of when they will receive it. . So now im stuck with a loaner and no eta on when parts will be available.

Reached the 100,000 mile mark and the truck started shuddering. Took it to the dealership and they tell me the torque converter is coming apart and I need a new transmission.

The truck ever since of bought it has been nothing but issues. Starting with the fuel pump issues then electrical issues and most recently the coolant flow control valve. This is my work truck and now I’m out of a truck with no loaner and the dealership has no eta.

Coolant control valve failure activating check engine light, reduced power mode and fan running continuously. Truck has been in the shop for 3 weeks already with no part available.