1. What component or system failed or malfunctioned, and is it available for inspection upon request? The failure involves the NOx emissions control system, specifically NOx Sensor #2 and the associated NOx catalyst/DPF assembly. Diagnostic trouble codes P11D5, P14D4, P22A1, P2832, P2833, and P28AF confirm abnormal NOx readings caused by sensor breakdown and catalyst performance degradation. Yes, the components are available for inspection at the servicing GM dealership. 2. How was your safety or the safety of others put at risk? A malfunctioning NOx sensor and catalyst can cause the vehicle to enter reduced‑power or limp‑mode operation, which may limit acceleration or speed unexpectedly. This can create hazardous situations during highway merging, passing, towing, or maintaining speed in traffic. Additionally, improper emissions control can lead to engine performance irregularities that may affect vehicle responsiveness. 3. Has the problem been reproduced or confirmed by a dealer or independent service center? Yes. The issue has been confirmed by a GM dealership through diagnostic testing. The dealer verified all fault codes and confirmed the NOx sensor failure and abnormal catalyst readings. 4. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives, or others? The vehicle has been inspected by GM‑certified dealership technicians. No inspections have been performed by police, insurance representatives, or other third parties. 5. 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 and emissions‑related warnings appeared around 80,000 miles, coinciding with the emissions warranty limit. Diagnostic trouble codes related to the NOx system were present, and the vehicle exhibited abnormal emissions readings consistent with sensor and catalyst malfunction.
2021 GMC Sierra 1500 engine complaints
Page 2 of 14: complaints 11 to 40 of 372, newest first, as owners wrote them.
2021 GMC with 6.2L motor. The engine begin to produce a clattering noise in the upper part of the engine. When the clattering happens the vehicle will shudder. I took the vehicle into a certified independent service center who diagnosed a catastrophic engine failure as a result of lifter and camshaft bearing failure. They further advised that this year of vehicle (2021) and engine (6.2L) was known to have this defect and might be subject to a safety recall. I contacted GM customer service who stated that my VIN was not included in the recall even though the year and engine matched the recall. I found that to be odd especially when I noted that nearly 600K vehicles matching my failed engine was recalled. She stated that I (owner) had to bear the cost of replacing the defective engine and labor. I had to have my vehicle transported from [XXX] to [XXX] at the cost of 1400 dollars. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
While towing a trailer on 6/26/26, the 6.2L L87 engine suffered a sudden drop in oil pressure, began knocking, and completely lost motive power on the roadway. Because the engine seized instantly, the vehicle experienced a sudden loss of power steering and power braking while managing the extreme weight of a trailer. This combination created a severe and immediate safety hazard, forcing me to maneuver a heavy, unpowered truck and trailer combination through active traffic to the shoulder without full steering or brake control, putting my life, my passengers' lives, and the safety of surrounding motorists at extreme risk. My dad read the codes before we took it to my mechanics and the only code I can remember is P0016. I took it and dropped it off at my local mechanics on 6/28/26. This is what my mechanic said: No Start-Truck came in not running. Had timing codes. I believe the crank bearing failed causing the engine to lose oil pressure. With the sudden loss of oil pressure, the timing chain tensioner slacked and caused the cam/crank to go out of time. Drained engine oil and found bearing material. We also cut oil filter open and found more bearing material. The timing cover was removed and verified the cam timing was off. In conclusion the engine has failed and will need full replacement. This is the exact failure mechanism under active the federal safety agency Investigation EA26005.
Vehicle is a 2021 GMC Sierra with 3.0 Diesel. Coolant control valve is bad. Vehicle has 108,000 miles. GM issued Bulletin N252508341 extending the warranty to 15 years or 150,000 miles for 2021-2022 GMC Sierra. Now they are saying my VIN # is not effected and they will not cover the replacement which costs about $2100. After researching this I'm finding many VINs are not covered and there are many trucks with failed parts that are not covered. GM should extend this to all VINs under those years. Its an obvious problem but their bulletin does not cover all the vehicles affected. They make it look like they are trying to make it right but in reality, its misleading.
Was just driving along and the car just died
The contact owns a 2021 GMC Sierra 1500. The contact stated that while driving and towing a 5,000-pound load, the vehicle made an abnormally loud sputtering sound at 3,000 RPM. The contact stated that the failure was more noticeable while towing a load. The vehicle was taken to an independent mechanic, where an audible diagnostic test was performed and the contact was informed that the sound was related to the engine bearings. The vehicle was then taken to the dealer, where it was diagnosed with fifty-two engine misfires. The contact was informed that the misfires should have caused the check engine warning light to illuminate; however, the light was not illuminated. The dealer replaced the ignition coils and spark plugs; however, the failure recurred while driving. The manufacturer was notified of the failure. The failure mileage was approximately 110,000.
Truck was in motion and the engine light started blinking then stopped. A couple miles down the road the truck jilted and the engine light came on again. The Service ESC and emergency parking brake light came on. The truck started shaking. We pulled over and parked. Turn off the truck and when we turned it back on it started shaking. When we drove we started hearing popping, knocking, loss in power of the vehicle. This could’ve caused serious damage to ourselves or other drivers if we could’ve have stopped. Vehicle is being inspected. Multiple same vehicles have had the same issues in my town. At least 5 that we know of. At one point all of the lights came on and now there is just a few lights. More than what I listed earlier.
Lifter collapsed at 31970 miles. It was fixed at GMC dealership. It just happened out of no where. No warning signs.
Received Re-Call for Engine Failure! Dealer replaced Engine Oil and Oil Cap @ 85,544 Miles. I read of the Re-call prior to the notice and I waited for it to come. After I received it and the Dealer made the changes, it made me afraid to leave town using my truck for fear of a breakdown on the Freeway. I use a Walker, so if I broke down and I was in the left lane and lost all power it would be very dangerous for me to get to the right side of the road! The truck started using excessive Oil after they changed the oil. I replaced four (4) quarts of oil @ 2526 miles! Speedometer reading 88070 miles.
1. I am being told that the high-pressure fuel pump (HPFP) catastrophically seized and locked up internally while driving. Because the HPFP on the 3.0L Duramax (LM2) engine is directly driven by the engine's timing system, this sudden mechanical seizure instantly destroyed the engine timing gears and snapped/skipped the timing chain. The failed components are currently intact inside the vehicle and are fully available for inspection upon request at Ron's Smith GMC in Merced, CA. 2. The failure occurred on busy Labor Day (XXX) while our family of [XXX] was traveling back home at 70 mph on a major highway. The truck violently shook, instantly lost all engine power, and forced the vehicle into a dangerous limp-mode state before completely stalling in live highway traffic at night around 10:45 pm. This sudden loss of propulsion at high speed severely compromised our ability to safely navigate out of the way of fast-moving highway traffic, creating an immediate & extreme risk of a high-speed rear-end collision. At times hazard lights didn't work causing family panic & screaming as truck shook with passing traffic. 3. The problem has been officially confirmed by Ron Smith GMC in Merced, CA. Their service department diagnosed the issue, confirming that the high-pressure fuel pump had locked up and subsequently destroyed the timing belt/chain & engine gears. 4. The vehicle and its failed components have only been inspected by technicians at the Ron Smith GMC dealership service department. No police, insurance representatives, or outside third parties have inspected the vehicle yet. 5. I had been extremely happy with my truck and there were absolutely no warning lamps, dashboard messages, or driving symptoms prior to the failure. The truck was operating perfectly normally under cruise until the exact moment of the failure, at which point a "Reduced Engine Power" warning flashed on the dashboard simultaneously with the mechanical lock-up, shaking, and immediate stall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF
1. I am being told that the high-pressure fuel pump (HPFP) catastrophically seized and locked up internally while driving. Because the HPFP on the 3.0L Duramax (LM2) engine is directly driven by the engine's timing system, this sudden mechanical seizure instantly destroyed the engine timing gears and snapped/skipped the timing chain. The failed components are currently intact inside the vehicle and are fully available for inspection upon request at Ron’s Smith GMC in Merced, CA. 2. The failure occurred on busy Labor Day (XXX) while our family of [XXX] was traveling back home at 70 mph on a major highway. The truck violently shook, instantly lost all engine power, and forced the vehicle into a dangerous limp-mode state before completely stalling in live highway traffic at night around 10:45 pm. This sudden loss of propulsion at high speed severely compromised our ability to safely navigate out of the way of fast-moving highway traffic, creating an immediate & extreme risk of a high-speed rear-end collision. At times hazard lights didn’t work causing family panic & screaming as truck shook with passing traffic. 3. The problem has been officially confirmed by Ron Smith GMC in Merced, CA. Their service department diagnosed the issue, confirming that the high-pressure fuel pump had locked up and subsequently destroyed the timing belt/chain and engine gears. 4. The vehicle and its failed components have only been inspected by technicians at the Ron Smith GMC dealership service department. No police, insurance representatives, or outside third parties have inspected the vehicle yet. 5. I had been extremely happy with my truck and there were absolutely no warning lamps, dashboard messages, or driving symptoms prior to the failure. The truck was operating perfectly normally under cruise until the exact moment of the failure, at which point a "Reduced Engine Power" warning flashed on the dashboard simultaneously with the mechanical lock-up, shaking, and immediate stall. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF
There is an known issue with the coolant control valve that causes the truck to enter "limp mode" that dangerously reduces the engine power. The part is not recalled but there is a special extended warranty, N252508341, up to 15yrs or 150,000 miles for 2021-2022 GMC 1500 trucks but my VIN is excluded from this for some reason. I would like this investigated.
The contact owns a 2021 GMC Sierra 1500. The contact stated that while the vehicle was parked, the battery charge indicator to zero. The vehicle lost motive power, and the vehicle was unable to exceed 30 MPH while driving. The vehicle was driven in LIMP Mode. The battery saver mode message was displayed before and during the failure. The vehicle then failed to restart. The vehicle had been repaired a year prior to the failure. The contact's blood pressure became elevated due to the issue. The failure mileage was approximately 98,000.
Excessive oil consumption. I am fearful that my vehicle engine will lock up.
On [XXX], my vehicle suffered a complete loss of propulsion on the highway, displaying fault codes P0324 and P0016. The vehicle was taken to Boyd's Tar Heel Chevrolet in Roxboro, NC, where the engine block was replaced under the official GM 6.2L engine safety recall.The truck was delivered back to me, and on the very first day I drove it—only 28 miles from my house—it suffered a secondary catastrophic loss of propulsion on the highway on [XXX]. The check engine light began flashing violently, indicating an immediate catalyst-damaging safety hazard, and the vehicle displayed fault code P0307 (Cylinder 7 Misfire).The dealership explicitly instructed me to stop driving the vehicle immediately, authorized the recovery, and told me to bill the tow directly to them. After towing the vehicle back to their facility, Boyd's Tar Heel Chevrolet reversed their position. They are now attempting to hold me financially responsible for the towing fees, along with spark plugs, wiring, and fuel injector services, claiming the failure is due to routine maintenance.This represents a severe highway safety hazard, a direct failure of the manufacturer's official recall remedy, and potential dealer misconduct to avoid liability under the active the federal safety agency Engineering Analysis EA26005 for post-recall 6.2L engine failures. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
While driving 40 MPH my entire dash lite up with every known light and the vehicle lost all power. The dealer stated I need an entire engine replacement, as with Many 6.2. My vehicle is 1 months out side of the recall, it has the exact symptoms and the exact damage as the recall.
Both of my upper ball joints wore out and one broke as I was driving down the road at 65 miles an hour pulling me into the on coming lane of traffic, there was no warning of this. I had both upper and lower ball joint replace. If there had been another vehicle coming in the on coming lane we would have had a head on collision. At an earlier date the motor in this same truck had a fallen lifter which cause my motor to loss power, I was able to take it to the local GM dealer and they fixed it, there was no warning this was happening either. I am worried I will have a catastrophic engine failure and GM will not cover this. I have looked up my
The contact owns at 2021 GMC Sierra 1500. The contact stated that while driving 60 MPH, the engine was overheating. The message "Reduce Engine Power" was displayed. The contact shifted to neutral to reach the dealer. The contact associated the failure with Special Coverage: N252508341; however, the VIN was not included. The dealer diagnosed the vehicle with coolant control valve failure, and the vehicle was repaired. The manufacturer was made aware of the failure and stated that the cost of the repair was not covered under the special coverage program. The failure mileage was approximately 94,328.
Check engine light came on my vehicle (104,000/mi) and fans came on while truck was off. Took to dealership and techs diagnosed vehicle as having bad "coolant flow control valve". Dealership ran VIN check as there is a GM "extended special coverage program" N252508341 for the LM2 motor, which my vehicle has. However, N252508341 only applies to vehicles in CA. The dealership did not cover my repair. I filed a complaint with GM who denied it due to the program being only applicable to CA trucks. I was advised to file a complaint with the federal safety agency as the only avenue with recourse. I would like if the federal safety agency intervened and made GM honor the program in all 50 states and I be offered a refund for the $2500.00 repair I had to pay for. Thank you.
Engine stop working, lots of black smokes through the exhausts and vibrating weird. Lifters failed amoung other parts and they deemed the engine bad so they replaced it with a new one. The new engine started to make the same weird noises.
Catastrophic engine failure at 77357 miles. I went to the local GM dealer and my VIN is not in the L87 engine recall. Not sure how to repair my truck , but feel like the engine should not have locked up with such low miles, and I done constant engine maintenance , meaning oil changes every 5K miles.
Catastrophic Engine Failure due to Lifter Failure at approximately 51,000 miles driven. This has been confirmed by the dealership and reported/escalated to General Motors. The truck is at the dealership for repairs. General Motors offered to cover 65% of the repair as a Goodwill sign. As the 60K powertrain warranty had expired. This truck has the same components that are covered under the recall for the same model year. However the recall only extends to March 1, 2021 Manufacture date. My truck was manufactured a few weeks prior to that so it was not included. GM refused even discuss this could be potentially due to a recalled issue. Multiple warning lights and error messaged were present on the dash indicating issues when it failed. Additionally, a loud metallic knocking noise was present at speed and idle. Power was significantly reduced and the engine was running very rough.
Engine I believe The truck died while I was doing 78 MPH on the highway Dashboard stated “shift into neutral and press start” I pulled to the side of the road and did what it stated and it would not crank over. I also put it in park turned the vehicle off and back on to try to start it. The lights on the dashboard, all gauges, the AC, and everything works the truck just will not crank over. Check engine light came on but is not throwing any codes
XXX 2021 GMC Seria 108,339 miles driving home from [XXX] in town and out of nowhere the lights on the dash light up I saw it say adaptive steering and something breaking. There was a lot going on as the steering was rapidly shaking limited breaking while trying to avoid a collision. The engine started a loud knocking sound and sudden smoking out tail pipes. I was able to get the truck stopped turned it off and sat there for a while trying to collect myself. Restarted the truck and slowly drove it to my home 2 miles away. It was flatbed to local GM dealer that quickly diagnosed it saying heavy smoke knocking needs New Engine! They won't confirm exactly what the internal engine failure is. Other than its Failed. The engine build date is 2020 day 350 My VIN is not currently in the current GM engine recall However it's certain this failure is totally related to GM's engineering design and Manufacturing issues. Look deeper into the recall date ranges this failure is clearly a victim. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Coolant Control Valve failure. This vehicle year is included in a GM bulletin that extends the Coolant Control Valve replacement coverage to 150K miles due to a faulty design. My is valve failing exactly as described in the bulletin and GM will not cover the replacement due to my vin number. The vehicle randomly goes into reduced power whereby it is prohibited from safely keeping up with traffic. Research shows that there are a significant number of owners in my same situation where GM is denying repair and replacement coverage.
Transmission failed, Value Body is listed by dealer as the cause. GMC is saying that my vehicle is not part of the recall, even though it is part of the same model, same years as well as the same problem, the value body on the transmission. See estimate from dealership Tucks GMC Hudson, MA TRANSMISSION REPLACEMENT WITH BYPASS VALVE $6800.00 RADIATOR REPLACEMENT LEAKING $1980.00 ABS TRACTION LIGHT WHEEL SPEED SENSOR $395.00 CHECK ENGINE LIGHT IS ON NEEDS PCV VALVE HOSE AND SOLENOID $430.00 OIL LEAK BETWEEN ENGINE AND TRANSMISSION ?
I was notified my lifters in my 6.2 L V8 would need to be inspected for any defects. When I purchased my vehicle from Car Max here in Jackson, MS, I received a notification from the dashboard that the engine oil was low and to add oil. I turned around and took it back to the dealership as soon as possible. This happened on the first day of owner ship with in 5 minutes of driving off from the lot. I Car Max told me to just add oil and bring them the receipt and they would reimburse me. I chose not to and asked them to service the vehicle to avoid any issues with my warranty or my Car Max Shield Warranty. 2,000 miles later the same notification came across the dashboard again. I took it back to Car Max immediately and they ended up sending it off to my local GM dealership for service. They topped it off with oil after inspecting it for any leaks in the engine. None were discovered. After the 3rd notification about the engine oil level being low after close to 3,000 miles, they serviced the vehicle and put the vehicle under the Oil Consumption Watch. This took place from October 2025 through September 2026. After multiple visits, they informed me they would need to perform further test to see if the lifters were failing and that I would be responsible for the labor fees estimated at around $632.82. I informed them I have Car Max’s 150,000 mile warranty. Fidelity Insurance company informed me they would need to send an inspector out to the GM dealership. Before this takes place, they would need the vehicle to undergo various tests and I would be responsible for the labor fees. Should the engine components be found worn down. Fidelity would not cover the repairs. Should the engine components be found defective, they would cover the replacement part but not the label. Labor costs would estimate around $2,978.95. I asked the GM dealership to share this information with me in writing for documentation purposes. I asked for my vehicle to be parked until further notice.
Lifter locked up causing bent push rod. This situation caused truck to strand the driver without warning. Truck needed to be towed. This repair was performed by the dealership and is a known issue with 6.2 L engine.
Loss of power, had engine repaired, replaced passenger side head and cylinder. Now drivers side is having the same issue.
Transmission stopped at 29,000 miles, engine died and was replaced at 32,000 miles
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