VinCanary

Reliability report · 2021 GMC Sierra 1500 · Updated July 2026

Watch the engine — first year of the big 6.2L failure recall, which hits Denali trims hardest.

2021 is where the engine story gets a headline. GM recalled roughly 597,000 trucks and SUVs with the 6.2L V8 (2021–2024) for connecting-rod and crankshaft defects that can cause sudden engine failure — federal investigators have expanded the probe twice. It's a free inspect-and-repair-or-replace remedy, and a completed recall (GM also moved these to 0W-40 oil) is reassuring on a used truck. Because the Sierra Denali skews to the 6.2L, it's especially exposed.

Underneath that, the 5.3L still has Dynamic Fuel Management lifter risk, and the 8-speed's costliest failure mode is covered by the 15-year/150,000-mile control-valve special coverage. So 2021 isn't a bad truck — it's one where the engine paperwork matters more than usual. If it's a 6.2L, the recall must be done; if it's a 5.3L, listen for lifters. Same truck under the skin — see the 2021 Silverado 1500 report.

Evidence: 506 NHTSA complaints · 7 recall campaigns · 6 mechanic & forum sources

Canary status

Squawking

What that means: The Sierra twin of the 2021 Silverado, where the recent file leans on the engine. 2021 is the first year of GM's nearly 600,000-truck 6.2L V8 recall for connecting-rod and crankshaft failure — a free inspect-or-replace fix that hits Sierra Denali disproportionately (the trim skews to the 6.2L) — while the 5.3L lifter issue continues.

CalmChirpingSquawkingFainted

506

Federal complaints

7

Recalls

$0

Under recall 25V274 (inspect/repair/replace)

Known issues

Ranked by the cost of ignoring them. Every claim carries its source.

6.2L V8 connecting-rod / crankshaft failure — recall 25V274

major

The defining 2021 issue if the truck has the 6.2L — and the Sierra Denali, which skews to that engine, is disproportionately affected. GM recalled about 597,571 vehicles (2021–2024 Sierra, Silverado, Tahoe, Yukon, Escalade) for connecting-rod and crankshaft defects that put debris in the oil and can cause sudden engine failure — 'no warning, just died' — with NHTSA expanding its probe twice. GM estimates roughly a 3% defect rate; the remedy inspects and repairs or replaces the engine free and moves to 0W-40 oil. A used 6.2L that's been through the recall is a known quantity; one that hasn't is an open question. Confirm completion by VIN.

What to check

Pink and cleanServiced. Proceed.

Dark brownDamage underway.

Under recall 25V274 (inspect/repair/replace)

$0

Sources: NHTSA complaint database, 2021 Sierra 1500 · NHTSA recall database and manufacturer communications (recall 25V274; transmission-valve coverage; eBoost CSP)

5.3L Dynamic Fuel Management (DFM) lifter failuremajor

If it's the 5.3L, the lifter issue rides on. DFM can deactivate any of all eight cylinders, and mechanics say its lifters fail more often and earlier than the older AFM — a tick, misfire, power loss, and a $3,000–$10,000 repair with no recall, only a class action and reactive warranty repairs. A DFM disabler (~$150) is cheap prevention and a cold-start tick is the walk-away sign. The 6.2L's risk is largely covered by its recall while the 5.3L's lifter risk is not — factor that into which one you buy.

Sources: NHTSA complaint database, 2021 Sierra 1500 · Independent mechanic transcripts (T1XX Silverado/Sierra; AFM/DFM lifter deep-dives)

~$150

DFM disabler module (preventive)

$3,000–$10,000

Lifter/valvetrain repair after failure

8-speed transmission — costliest failure is coveredmoderate

The 8-speed can still shudder and shift harshly, but the expensive control-valve failure is covered on this year by GM's 15-year/150,000-mile Special Coverage (from the in-service date, regardless of ownership) — a new valve body free, with reimbursement for prior repairs. The 10-speed on other trims is the stronger unit. Test-drive for shudder and confirm the coverage window.

Sources: NHTSA recall database and manufacturer communications (recall 25V274; transmission-valve coverage; eBoost CSP) · Independent mechanic transcripts (T1XX Silverado/Sierra; AFM/DFM lifter deep-dives)

$0

Control valve under 15yr/150k coverage

Rear sliding-window leaks and MultiPro tailgatemoderate

Two things to check on a 2021 Sierra. The power sliding rear window (2019–2022 crew cabs) can leak where the sliding pane meets the frame, wetting the headliner and window electronics; GM replaced windows under warranty but leaks can return. And the Sierra-exclusive MultiPro powered tailgate has drawn reports of abrupt operation — exercise every function. Check the rear headliner and floor for staining and musty smell.

Sources: NHTSA complaint database, 2021 Sierra 1500

eBoost brake unit — Customer Satisfaction Programminor

GM ran a Customer Satisfaction Program for certain 2021 trucks whose eBoost brake unit assemblies could develop brake-function issues over time, replacing the unit free. It's a targeted program rather than a widespread failure — worth a VIN check to see whether it applied and was done.

Sources: NHTSA recall database and manufacturer communications (recall 25V274; transmission-valve coverage; eBoost CSP)

Nearly 600,000 trucks with the 6.2L V8 were recalled — connecting rods and crankshaft, debris in the oil. No warning, just died.
6 mechanic & owner sources

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Open recalls

Free fixes at any GMC dealer. Run the VIN — “completed” isn’t always completed.

  1. 25V2746.2L V8 connecting rod/crankshaft manufacturing defect can cause engine failure (2021–2024 Sierra); inspect and repair or replace the engine free, switch to 0W-40 oil.open
  2. 20V792Front-center seat-belt bracket may not be secured to the seat frame (2019–2021); inspected/reassembled free.open
  3. 20V811Incorrect bolts may have been used to secure seat belts (2021 Sierra 1500); suspect bolts replaced free.open
  4. 20V684Continental tires may be overcured and can fail (2020–2021); inspect/replace as needed, free.open
  5. 21V98517-inch spare may be incompatible with certain accessory wheels, affecting ABS (2019–2021); free.open
  6. 24V797Diesel-only: transmission control valve can fail and lock the rear wheels (2020–2022 diesel); software updated free, plus special coverage.open
  7. 26V083Re-inspection for diesel trucks possibly repaired incorrectly under 24V797; transmission control software updated free (2020–2022).open

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