2021 GMC Sierra 1500
Problems, recalls and owner-reported issues
Engine is the leading concern among 572 owner complaints filed for this model year. This is the 5th highest complaint count among 26 Sierra 1500 model years with reports.
Of the 2021 reports, 5 involved a crash and 6 involved a fire. 2 people were injured.
What owners report most often
Recalls and investigations
Power train, automatic transmission, control module, softwareFeb 12, 2026
General Motors, LLC is recalling certain 2020 Chevrolet Silverado 2500, 3500, GMC Sierra 2500, 3500, and 2020-2022 Chevrolet Silverado 1500 and GMC Sierra 1500 vehicles that may have been repaired incorrectly under recall 24V797. The transmission control valve may fail and cause the rear wheels to lock up.
Rear wheel lock up increases the risk of a crash.
Dealers will inspect the vehicles and update the transmission control software, free of charge. Owner notification letters were mailed March 6, 2026. Owners may contact GMC customer service at 1-800-462-8782 or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N252516560. Vehicle Identification Numbers (VINs) involved in this recall became searchable on NHTSA.gov on February 12, 2026.
Campaign 26V083000 on NHTSA.gov
Engine and engine cooling, engine, hard parts internal/mechanicalApr 24, 2025
General Motors LLC (GM) is recalling certain 2021-2024 Cadillac Escalade and Escalade ESV, Chevrolet Silverado 1500, Suburban, and Tahoe, GMC Sierra 1500, Yukon, and Yukon XL vehicles equipped with a 6.2L V8 gas engine. The connecting rod and/or crankshaft engine components may have manufacturing defects that can lead to engine damage and engine failure.
Engine failure increases the risk of a crash.
Dealers will inspect the engine, and as necessary, repair or replace the engine. For vehicles that pass inspection, dealers will add higher viscosity oil, install 6 oil fill cap, replace the oil filter, and update the owner's manual. Repairs will be performed free of charge. Owner notification letters were mailed June 18, 2025. Owners may contact Cadillac customer service at 1-800-333-4223, Chevrolet customer service at 1-800-222-1020, or GMC customer service at 1-800-462-8782. GM's number for this recall is N252494000.
Campaign 25V274000 on NHTSA.gov
Power train, automatic transmission, control module, softwareOct 24, 2024
General Motors, LLC (GM) is recalling certain 2020-2022 Chevrolet Silverado 1500, 2500, 3500, GMC Sierra 1500, 2500, 3500, 2021 Cadillac Escalade, Escalade ESV, Chevrolet Tahoe, Suburban, GMC Yukon, and Yukon XL vehicles equipped with diesel engines. The transmission control valve may fail and cause the rear wheels to lock-up.
Rear wheel lock-up can increase the risk of a crash.
Dealers will install new transmission control module software, free of charge. GM will provide a special coverage program to cover the repair of transmissions that are identified by the remedy software as containing a defective control valve. Owner notification letters were mailed December 12, 2024. Owners may contact GM customer service at 1-888-988-7267, Cadillac customer service at 1-800-458-8006, GMC customer service at GMC 1-800-462-8782 or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N242454440.
Campaign 24V797000 on NHTSA.gov
Tires, temporary/emergency spare tireDec 16, 2021
General Motors (GM) is recalling certain 2019-2021 GMC Sierra 1500 and Silverado 1500 vehicles equipped with certain accessory road tires and a 17" spare tire. The 17" spare tire provided with the vehicle is not compatible for use with the accessory wheels, which can cause the anti-lock brake system (ABS) to not function properly under certain conditions.
An ABS system that does not function properly can increase the risk of a crash.
Dealers will provide a new 17" spare tire and wheel assembly that is compatible with the accessory wheels, free of charge. Dealers will also apply a new spare tire information label, and provide owners with an owner's manual insert clarifying which spare tire to use with the accessory road tires and with the 17" original tires. Owner notification letters were mailed February 7, 2022. Owners may contact GM customer service at 1-800-462-8782 or GMC customer service at 1-800-462-8782. GM's number for this recall is N212346510.
Campaign 21V985000 on NHTSA.gov
Seat beltsDec 23, 2020
General Motors, LLC (GM) is recalling certain 2020 Chevrolet Bolt EV and 2021 GMC Canyon and Sierra 1500, 2500 and 3500, Yukon, Yukon XL, Cadillac Escalade and Escalade ESV and Chevrolet Blazer, Camaro, Colorado, Equinox, Silverado 1500, 2500 and 3500, Suburban and Tahoe vehicles. Incorrect bolts may have been used at one or more fastening locations to secure the seat belts to the vehicle. If an incorrect bolt was used, the seat belt may not be properly attached to the vehicle.
If a seat belt assembly is not properly attached to the vehicle, the seat belt may not properly restrain an occupant in the event of a crash, increasing the risk of injury.
GM will notify owners, and dealers will replace the suspect bolts, free of charge. The recall began January 29, 2021. Owners may contact GMC customer service at 1-800-462-8785, Cadillac customer service at 1-800-458-8006, or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N202322230.
Campaign 20V811000 on NHTSA.gov
Seat beltsDec 17, 2020
General Motors, LLC (GM) is recalling certain 2019-2021 Chevrolet Silverado 1500 and GMC Sierra 1500, 2021 Chevrolet Suburban and Tahoe and GMC Yukon XL and 2020-2021 Chevrolet Silverado 2500 and 3500 and GMC Sierra 2500 and 3500 vehicles. The seat belt brackets may not be secured to the seat frame in the front-row center seating position.
If a seat-belt bracket is not secured, the seat belt may not properly restrain an occupant in the front-row center seat position, increasing the risk of injury in a crash.
GM will notify owners, and dealers will inspect left-side and right-side front-row center seat-belt bracket attachments and reassemble it correctly as necessary, free of charge. The recall began January 26, 2021. Owners may contact GMC customer service at 1-800-462-8782, Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N202314670.
Campaign 20V792000 on NHTSA.gov
TiresNov 5, 2020
General Motors LLC (GM) is recalling certain 2020 Buick Enclave, Cadillac XT5, GMC Acadia and Chevrolet Traverse vehicles and 2020-2021 Chevrolet Silverado 1500, GMC Sierra 1500 vehicles. The vehicles may have been manufactured with Continental tires that were overcured.
Overcured tires may experience a carcass break in the sidewall resulting in a sudden air loss or could develop a belt edge separation which could lead to partial or full tread/belt loss. Either condition increases the risk of a crash.
GM will notify owners, and dealers will inspect vehicles and replace tires that have DOT number and production mold number combinations identified by Continental, free of charge. The recall began December 17, 2020. Owners may contact GMC customer service at 1-888-988-7267, Buick customer service at 1-866-608-8080, Chevrolet customer service at 1-800-222-1020 or Cadillac customer service at 1-800-458-8006. GM's number for this recall is N202319030.
Campaign 20V684000 on NHTSA.gov
Representative owner complaints: power train
137 reports, newest first. Show all
Power train, Engine, Nov 2, 2025
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.
Power train, Other or unspecified, Engine, Oct 19, 2025
This was the first time I had ever experienced the rear differential locking up at highway speeds in my truck. It was probably the day after I bought the truck. I was going down route one southbound going probably around 60 miles an hour and the wheels locked up and the vehicle felt like it was gonna come to a screeching hole. It felt like I hit something And then the wheels unlocked and it allowed me to keep driving. I thought that I might have hit the cruise control button on the steering wheel by accident and chopped it up to operator error which now I know is one of the most dangerous recall issues I’ve ever had to experience or indoor. Thank goodness my family was not with me at the time. But these issues continued on for months…
Power train, Other or unspecified, Engine, Oct 19, 2025
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.
Power train, Vehicle speed control, Engine, Oct 19, 2025
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….
Power train, Vehicle speed control, Engine, Oct 14, 2025
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?
Power train, Oct 8, 2025
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.
Power train, Oct 3, 2025
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.
Power train, Oct 1, 2025
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.
Power train, Engine, Sep 24, 2025
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”
Power train, Sep 19, 2025
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
Power train, Sep 18, 2025
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.
Power train, Sep 16, 2025
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
Power train, Sep 8, 2025
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.
Power train, Engine, Aug 28, 2025
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
Power train, Engine, Aug 13, 2025
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.
Power train, Aug 1, 2025
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.
Power train, Engine, Fuel/propulsion system, Jul 25, 2025
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.
Power train, Jul 22, 2025
AT AROUND 60,000 MILES I HAD EXPERIENCED SHUTTERING AND JERKING IN LOW GEARS AND THE VEHICLE SHOOTS FORWARD WHEN COMING TO A COMPLETE STOP. I WAS ABLE TO TAKE THE VEHICLE IN A SHORT TIME AFTER AND I WAS TOLD BY THE DEALERSHIP THAT IT NEEDED A TRANSMISSION FLUSH. I COMPLETED THE FLUSH AND AFTER A WEEK OR TWO IT STARTED DOING IT AGAIN. I TOOK IT TO A TRANSMISSION SHOP AND THEY ADVISED IT IS THE TRANSMISSION VALVE BODY THAT IS BAD. I BELIEVE THIS STARTED HAPPENING BEFORE MY WARRANTY WAS OUT BUT DUE TO ME BRINGING IT IN AFTER THE MILEAGE THEY WOULD NOT HONOR THE WARRANTY. THIS COULD CAUSE MULTIPLE HAZARDS AT STOPS AND WHILE DRIVING. NO WARNING LAMPS OR MESSAGE HAVE EVER APPEARED.
Power train, Engine, Jul 21, 2025
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.
Power train, Engine, Jul 18, 2025
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)
Power train, Engine, Jul 12, 2025
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.
Power train, Jul 9, 2025
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.
Power train, Jul 8, 2025
The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 75 MPH, the vehicle jerked and downshifted to overdrive. The message "Engine Power Reduced" was displayed on the instrument panel. The driver depressed the accelerator pedal, but the vehicle failed to exceed 4 MPH. The vehicle was taken to the dealer, where it was diagnosed that the valve body failed, which caused the transmission to fail. The vehicle was repaired. While the contact was driving home after the vehicle was picked up, the vehicle jerked and hesitated. The dealer was contacted and informed the contact that if the check engine warning light becomes illuminated the vehicle could be diagnosed. After several days, the check engine warning light illuminated, and the vehicle was taken to the dealer where it was diagnosed that the shutter valve had failed and needed to be replaced. The vehicle was repaired. The contact stated that the failure persisted. The contact received NHTSA Campaign Number: 24V797000 (POWER TRAIN). The vehicle was repaired; however, the failure persisted. The manufacturer was made aware of the failure and offered the contact assistance with the transmission repair. The failure mileage was approximately 119,000.
Power train, Jul 1, 2025
My 2021 GMC Sierra 1500 Diesel Truck is displaying the Check Engine Light which I was told by the local Mount Vernon GMC Dealership is a failed Temperature Control Valve affecting the transmission. I also get a warning message of "Reduced Engine Power". I am told that it is OK to drive the vehicle but at reduced power. The dealership told me they ordered a replacement part which is covered under warranty on May 7, 2025, but showed on "Back Order". Every time I call to follow up on the status, I'm told it is still on "Back Order", and they cannot do anything to improve the delivery. Why does a customer, owning a "Denali" truck under warranty, can't get the problem resolved? I have a recall notice from GMC dated January 2025 about this very problem and have shown it to GMC dealerships during regular services, and still have the problem. Since I have bought this truck, I have experienced a failed right running board that cost $1,500 to repair a few months ago which is failing again. The driver side mirror now vibrates when I put the truck into drive after being in reverse, and I cannot get any idea on when this transmission valve problem will be fixed which is causing me serious delays in using the truck to pull a trailer. Prior to this problem I had the dealership replace my brakes which required 2 follow-up repairs due to the "GMC original rotors" being warped that required machining to make them not vibrate which to me, now makes them "used". This means I paid full price for "repaired" parts! I thought that by buying a GMC "Denali" 1500 Sierra truck I was buying the "top of the line" in pick-up trucks but now finding out it's a lemon. I love the truck, but not the problems. What do I need to do to get this fixed? [XXX] [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Power train, Jun 24, 2025
In December of 2024 the engine started not being able to reach full power. This would happen intermittently and there would be a check engine light that would come on when this was happening. In January of 2025 I had the code pulled up by a mechanic at a local shop and this mechanic actually spoke to the service manager of the GMC dealership who said it was covered under the 100,000 mile power train warranty. I took it to the dealership who then told me the diesel mechanic was backed up and I would have to schedule repair for February. I had also received a recall notice in the mail for another issue so asked about taking of both things at the same time. I made the appointment for mid-February so had to deal with reduced engine power for several weeks.The dealership had my truck for several days and a recall was fixed and I thought the reason for the reduced engine power had been fixed also. I had received a phone call from the service representative about an issue that would cost over $1200 that I declined. I did not realize that this was actually for the main issue. I was still thinking the reduced engine power was under warranty. I got my truck back but then the next day the check engine light came on again and the engine power was reduced again. I immediately called the service representative who then told me only the recall had been fixed and that the reason for the reduced engine power was not fixed because I had declined the service. I was totally confused and didn’t understand what happened. This is when I was told that the reason for the reduced engine power was due to a coolant control valve, which was not under the powertrain warranty. I pushed the issue and wanted answers as to why the service manager himself told the mechanic that it was under warranty and was told that the service manager is not a technician and they rely on what the technician says is the problem. And this problem was not covered. I finally gave in and got it fixed and paid $1788.