Faulty lifters replaced on passenger side. Had only 25000 miles on engine. GM extended warranty on thousands with this engine but not mine. Have only 28000 miles on truck and just turned 5th year so warranty is void. GM should extend warranty on all vehicles with this engine.
2021 GMC Sierra engine problems
moderate 213 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
213
Recalls
0
Avg fix
$3,100
2fires
When does it fail?
Of the 213 engine complaints filed for the 2021 GMC Sierra, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Engine accounts for 42% of every owner complaint on file for this vehicle — the dominant problem area across 10 categories tracked.
Owners have filed 213 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
The failure pattern owners describe
The 2021 GMC Sierra has systemic engine problems across multiple powerplants. The 6.2L gasoline V8 is subject to a massive GM recall (N2524944000/25V274, April 2025) affecting 650,000+ vehicles from 2019–2023 for catastrophic bearing and connecting rod failure. Owners report sudden engine seizure without warning at mileages ranging from 1,000 to 95,000 miles—sometimes with only seconds of warning (low oil pressure light). One owner nearly hit oncoming traffic when the engine shut off on a mountain road with a guardrail; another was stranded with a 9-month-old in the car. Metal shavings in the oil, loud rod knock, and complete loss of propulsion are consistent failure signatures. GM initially promised engine replacement, then switched to a PicoScope diagnostic test; if it "passes," owners get an oil viscosity bump and new cap (reported <10% effective). Replacement engines themselves have failed with the same defect.
The 3.0L diesel coolant control valve fails suddenly, dropping highway speed from 70 mph to 50 mph without driver input—dangerous on interstate. One owner was three hours from home when it happened. The part is backordered nationwide with no interim fix.
Smaller gasoline engines suffer DFM lifter failures starting as low as 7,000 miles, requiring full engine teardown or replacement. One dealer had four identical trucks in queue simultaneously, with 3–4 month parts waits. No-start conditions plague diesel models despite three software updates since purchase. Excessive oil burning and leaking appear chronic.
Across all powerplants, dealers are swamped, parts are unavailable, and GM has not authorized loaner vehicles or extended coverage in most cases. Owners report being told to keep driving unsafe vehicles, wait indefinitely for parts, or pay tens of thousands out-of-pocket.
Same GMC Sierra engine reports on nearby years: 2019 · 2020 · 2022 · 2023 · 2024
Failure modes owners describe
6.2L gasoline engine bearing/rod failure and catastrophic seizure
Internal bearing or connecting rod failure causing sudden loss of oil pressure, engine seizure, and complete loss of propulsion without warning. Metal shavings found in oil. Affects 2019-2023 models with 6.2L V8; massive GM recall N2524944000/25V274 issued April 2025 with 650,000+ vehicles affected.
When: Variable mileage; some as low as 1,000 miles, others 20,000-95,000 miles. Incidents reported across 2021 production year.
Symptoms owners cite: Sudden loud knocking or rod knock sound from engine; Abrupt loss of engine power while driving; Engine shuts off without warning; Low oil pressure warning light illuminates (sometimes only seconds before failure); Engine seizes and will not restart; Metal shavings visible in oil and oil filter; Smoke from engine or exhaust; No warning signs prior to catastrophic failure in many cases
Codes mentioned: P0300 (random/multiple misfire), P0302 (cylinder 2 misfire)
Repairs/costs cited: Full engine replacement required. Parts unavailable as of reports through June 2025. Dealers report months-long backorder. Some owners facing $11,000-$12,000+ for crate engine replacement. Replacement engines themselves have failed in some cases, placing same defect back in vehicle.
Recalls/TSBs owners mention: GM Recall N2524944000 (NHTSA 25V274) issued 4/23/2025. Initially stated engines would be replaced based on build date; later changed remedy to PicoScope diagnostic test—if it passes, only oil viscosity upgrade and new cap applied (reported <10% success rate). Warranty coverage unclear; dealer states VIN outside recall range despite matching failure pattern. Tools for evaluation were not yet developed as of late June 2025. Special Coverage program N252508341 for 3.0L Duramax extends to 15 years/150k miles but some owners told they do not qualify. No loaner/rental assistance or extended warranties offered.
3.0L Duramax diesel coolant control valve failure
Failure of the coolant control valve (part #24001355) causing sudden loss of power while driving and unsafe reduction in engine speed on highway. Creates safety hazard when vehicle speed drops from 70 mph to 50 mph without driver control. Confirmed by independent mechanic and authorized dealership.
When: Reported at 51,000 miles; failure occurred when AC was on in summer conditions. Began July 2025.
Symptoms owners cite: Sudden loss of engine power while driving at highway speed; Vehicle speed limited to approximately 50 mph despite throttle input; AC takes long time to cool down or shuts off; Engine fan runs loudly or stays on after vehicle shut off; Check engine light illuminates; Message 'A/C Off Due To High Engine Temp' appears on display; Engine not overheating despite symptoms (normal temperature gauge readings)
Codes mentioned: P1098, Service Bulletin 25-NA-185 (revised 12/4/2025)
Repairs/costs cited: Coolant control valve replacement required. Part on national backorder; dealer states 2+ month wait. No interim solution offered.
Recalls/TSBs owners mention: GM Service Bulletin 25-NA-185 (revised 12/4/2025) addresses this exact failure on 2021-2026 3.0L Duramax trucks. Special Coverage program N252508341 extends coverage to 15 years/150k miles when diagnostics confirm failure. However, owners report being told their specific VIN is not covered under warranty despite documented failure matching bulletin criteria.
DFM lifter assembly and camshaft/valve train failure
Failure of Dynamic Fuel Management lifters, camshafts, or valve train components causing severe engine noise and internal damage. Requires engine disassembly and replacement of multiple valvetrain parts. Occurs in small-block V8 engines with DFM/AFM feature. Industry reports and class action lawsuits indicate failures recur even after repair.
When: Reported at 7,000-22,000 miles on new vehicles. One case at 15,873 miles on freeway.
Symptoms owners cite: Loud ticking, knocking, or rattling noise from engine; Engine noise only under light acceleration or at low RPM initially; Rough idle or rough running sensation; Check engine light illumination; Engine shuddering at highway speeds; Misfires detected; Abnormal noise from engine during acceleration and deceleration; Engine failure or inability to accelerate as intended
Codes mentioned: Service Update N212353840, PIP5776, Technical Service Bulletin 19-NA-219
Repairs/costs cited: Requires replacement of lifter assembly, camshaft, valves, push rods, and valve train components. One case documented $12,360 replacement cost including labor. Dealers report 3-4 month parts backorder. One dealer had 3-4 other trucks with identical problem in queue simultaneously. Repairs not immediately available; vehicles left stranded.
Recalls/TSBs owners mention: GM issued Technical Service Bulletins (N212353840, PIP5776, 19-NA-219) and product communications acknowledging lifter failures in Gen V small-block V8 with DFM/AFM. Some coverage under powertrain warranty for initial repair. However, no extended warranty or special coverage offered. Owners requesting 10-year/100k-mile extension to protect against recurrence, which industry data shows is common.
Excessive oil consumption and leaking
Engine consuming oil at abnormal rate (up to 15 quarts in 2 months or 5 quarts at a time) combined with oil leaks from pan, rear main seal, or other locations. Low oil pressure warning light illuminates. One case involved failed alternator and crankshaft hoses secondary to oil leaks.
When: Reported at 44,000 miles, 51,000 miles, and various other mileages. New vehicles consuming oil rapidly within first few months of ownership.
Symptoms owners cite: Low oil pressure warning light illuminates while driving; Oil odor while driving; Visible oil leaking onto ground; Rod knock noise developing from oil starvation; Engine fan running loudly due to thermal stress; Vehicle messages indicating low oil requiring frequent refill
Repairs/costs cited: Rear main seal gasket replacement attempted but did not resolve leaking in one case. Subsequent failures of alternator and crankshaft hoses due to oil exposure. Cost for alternator and hose replacement charged to owner; rear main seal covered under warranty. Dealers performed oil consumption tests but did not complete testing in some cases.
Recalls/TSBs owners mention: Dealer instructed some owners that higher viscosity oil should be used (moved to thicker grade during recall remedy testing). No root cause correction identified. Manufacturer notified but no assistance provided beyond warranty coverage for some parts.
No-start condition with engine cranking/screeching followed by shutdown
Vehicle fails to start on ignition button press; engine screeches or cranks for 20-45 seconds before powering off completely. After 10-minute wait, vehicle starts normally. Occurs repeatedly (approximately 15 times in 2025 alone) with no simultaneous check engine light or fault code. No diagnostic code appears during failure events.
When: Recurring issue from 2021 purchase through January 2024 (approximately 10 occurrences), increased frequency in 2024 (similar frequency), and approximately 15 occurrences in 2025.
Symptoms owners cite: Engine screeches loudly during attempted start; Extended cranking (20-45 seconds) on ignition button press; Vehicle powers off entirely after extended crank attempt; Vehicle will not start after single attempt; Vehicle starts normally after 10-minute wait; No check engine light during failure; No fault codes generated during failure event; Battery replaced at owner expense (October 2024) per dealer recommendation without resolving issue
Repairs/costs cited: Battery replacement (October 2024) at owner expense did not resolve recurring issue. Third software update in December 2025 intended to resolve but problem persisted.
Recalls/TSBs owners mention: Dealer attributed issue to vehicle battery and recommended replacement (October 2024). GM advised software update would resolve issue. Software update applied December 2025 but problems continued. Issues explicitly explained to service technicians during 2025 recall repair visit with no resolution.
Engine stall and reduced power mode while driving
Engine stalls or enters limp mode (reduced power) suddenly while driving at highway speeds with no warning, forcing vehicle to 50 mph or lower. In some cases, vehicle cannot be restarted immediately. Dangerous when occurring on high-speed roadways.
When: Reported at various mileages including 70,000 miles, multiple times in same vehicle. One incident during first 1-2 miles of trip.
Symptoms owners cite: Sudden engine stall while driving; Check engine light illuminates (sometimes blinking); Vehicle enters reduced power/limp mode limiting speed; Message 'Shift into Neutral to Restart' displayed; Message 'Pull Over Immediately' displayed on DIC; Vehicle does not restart immediately after stall; No prior warning signs before failure; Vehicle must be restarted via fuel pump delay or wait period
Codes mentioned: P1006 (multiple instances in one case)
Repairs/costs cited: Root cause not always diagnosed. One case attributed to failed bearing requiring engine replacement. Dealers attribute to various causes including coolant system faults. Towing required in multiple cases.
Recalls/TSBs owners mention: Vehicles under recall 25V274 but parts not yet available for repair as of latest reports. Roadside assistance offered in some cases but communication difficult. GM indicates recall repair could take months. One case noted vehicle towed and left unrepaired for 2+ months awaiting parts.
SCR NOx catalyst and EGR cooler efficiency faults (diesel)
Diesel Duramax engine displaying repeated check engine light for SCR NOx catalyst efficiency and EGR cooler efficiency below threshold. Same diagnostic codes reappear after multiple service visits and software updates spanning years (2021-2025).
When: First purchased 2021, codes appearing intermittently through 2024, approximately 30 occurrences in 2025 alone confirmed by at-home diagnostic scanning.
Symptoms owners cite: Check engine light illuminates approximately 30 times in 2025; SCR and EGR diagnostic codes repeat despite repairs; Codes appear and disappear intermittently; No improvement after third software update (December 2025)
Codes mentioned: P2C7A (SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 2), P14D9 (Exhaust Gas Recirculation Cooler Efficiency Below Threshold)
Repairs/costs cited: Three software updates attempted to resolve since 2021; same codes reappear. Multiple dealership visits and diagnostic evaluations performed without resolving underlying issue.
Recalls/TSBs owners mention: GM instructed dealers to perform software updates (third one in December 2025). No alternative remedy identified despite years of warranty coverage visits.
Fire hazard from engine compartment
Engine compartment fire or flame appearance indicating serious internal combustion or electrical failure. One vehicle caught fire on driver's side near rear wheel while in motion.
When: Reported at approximately 2,800 miles on new vehicle.
Symptoms owners cite: Abnormal noise from engine compartment; Explosion sound from engine area; Flames visible from engine compartment or wheel area; Smoke and flames requiring fire extinguisher use
Repairs/costs cited: Engine replaced under warranty. Vehicle repaired but owner feels unsafe driving it.
Recalls/TSBs owners mention: Engine failure covered under warranty and replaced. Vehicle was repaired at dealership Quality Buick GMC (Albuquerque, NM) but manufacturer investigation did not result in additional remedies or communications about safety.
Diesel fuel gelling in filter housing during cold weather
Diesel fuel gels up specifically in the fuel filter housing during freezing conditions (3°F reported), causing vehicle to enter reduce power mode and stall. Owner used Top Tier diesel per manual but additives apparently needed in some regions. Design flaw appears endemic to fuel filter housing insulation.
When: Winter driving condition reported at 3°F ambient temperature.
Symptoms owners cite: Reduce power mode display on dashboard; Vehicle immediately shuts off; Vehicle will not restart after stall; Fuel gelling only in filter housing, not fuel tank (due to volume advantage of tank)
Repairs/costs cited: No repair attempted; issue resolved after engine cooled. Design flaw requires improved insulation or heating to fuel filter housing.
Recalls/TSBs owners mention: No action taken by GM to improve fuel filter housing design or provide heating element solution. Owner's manual recommends Top Tier diesel but does not recommend required additives in freezing climates. Pattern appears common in diesel trucks per owner research.
Synthesized from 213 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 8 most recent
Traveling on interstate going at the posted speed limit and turned off the interstate onto my exit turn and vehicle engine started knocking and engine shut off oil warning light came on all while trying to stop the vehicle at the cross traffice stop sighn and ended up stopped in the middle of another highway barley missing the cross traffic coming at me from both directions. This happened at i94…
Famous lifter issue in the l84 engine. Hundreds of documented complaints and current class action lawsuit. I had to stop on a busy highway and it caused unsafe passing and irritated humans.
Complete engine power loss.
The contact owns a 2021 GMC Sierra 1500. The contact stated while driving 15 MPH and making a turn, the vehicle lost power steering assist functionality. Additionally, the brake pedal was depressed several times but failed to respond. The parking brake, traction control, brake, engine, and headlights warning lights were illuminated. The contact also stated that the warning message "Limited Power"…
mechanical and electrical issues with my GMC Sierra Elevation Duramax Diesel, purchased in 2021. Despite multiple dealership visits, diagnostic evaluations, repairs, and software updates, these issues persist and have significantly impacted the reliability and safety of the vehicle. In December 2025, my vehicle was taken to the dealership for diagnostics and a third software update intended to…
15000 miles lifter failure in traffic highway at speed 70 MPH lost power engine failed multilane highway rush hour traffic no warning failure
The vehicle was bought brand new and was only driven for a week. It was in motion on the freeway when the engine started to sound noisier than usual, like that of an older truck. It was hard to notice on higher speeds on the freeway, but upon slowing down on curves, it got more obvious that something was really wrong because the noise sounded like something was loose inside the engine. There…
Had engine trouble with your 2021 GMC Sierra?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2021 GMC Sierra?
It's a documented issue but not catastrophic. 213 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Across the 50 complaints that reported odometer mileage, most engine failures cluster between 32,000 and 83,000 miles, with the median around 50,000. A quarter of owners report trouble before 32,000; a quarter make it past 83,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2021/GMC/Sierra.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.