The Lemon Index2021 GMC Sierra.
The 2021 GMC Sierra is better than average by owner complaints: 183 complaints in its first 3 years and a Lemon Index of 76, where 100 is the average car. Owners complain most about engine, it has 7 recalls, and it gets 16 to 26 mpg combined. The best GMC Sierra year is 2010.
Before you buy. What matters most for this car.
How serious. Out of 663 owner complaints, owners reported:
Every GMC Sierra year. 2021 is highlighted. Lower is better.
What owners complain about most. From owner complaints to the government.
Share of this year's owner complaints filed with NHTSA, not the share of cars that break. One complaint can name more than one area.
When owners reported problems. From owner complaints to the government.
Most owners who filed a complaint with NHTSA had 23K to 81K miles on the car (141 complaints listed the miles). This shows when people who had a problem reported it, not the odds that your car will have it.
- engine complaints mostly came at 15K–98K miles
- transmission & drivetrain complaints mostly came at 38K–111K miles
- electrical complaints mostly came at 2K–63K miles
Recalls 7
- transmission & drivetrain 2026
The transmission control valve may fail and cause the rear wheels to lock up.
- engine 2025
The connecting rod and/or crankshaft engine components may have manufacturing defects that can lead to engine damage and engine failure.
- transmission & drivetrain 2024
The transmission control valve may fail and cause the rear wheels to lock-up.
Show all 7 recalls
- tires 2021
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.
- seat belts 2020
Incorrect bolts may have been used at one or more fastening locations to secure the seat belts to the vehicle.
- seat belts 2020
The seat belt brackets may not be secured to the seat frame in the front-row center seating position.
- tires 2020
The vehicles may have been manufactured with Continental tires that were overcured.
Recall repairs are free at any dealer. A recall only matters if it's still open on that exact car, so check its VIN.
Problems GMC told dealers about
GMC sent dealers 1648 repair notes for this car. The ones about its biggest problems:
- This informational bulletin provides information on Transmission Adaptive Functions and…
Ask a seller or mechanic if these were done. Some are free under warranty or a special program.
Government investigations
- OpenLoss of motive power due to engine failure post recall remedy2026
- OpenLoss of motive power due to engine failure2025
- ClosedLoss of motive power due to engine failure post recall remedy2026
- ClosedLoss of motive power due to engine failure2025
NHTSA looks into a problem when enough owners report it. Many end in a recall.
Safety
Crash test details
| Version | Overall | Front | Side | Rollover |
|---|---|---|---|---|
| GMC Sierra 1500 PU/CC 4WD | ★★★★☆ | ★★★★☆ | ★★★★★ | ★★★★☆ |
| GMC Sierra 1500 PU/EC 4WD | ★★★★★ | ★★★★☆ | ★★★★★ | ★★★★☆ |
| GMC Sierra 1500 PU/RC 4WD | ★★★★★ | ★★★★☆ | ★★★★★ | ★★★★☆ |
| GMC Sierra 1500 PU/CC 2WD | ★★★★☆ | ★★★★☆ | ★★★★★ | ★★★★☆ |
| GMC Sierra 1500 PU/EC 2WD | ★★★★★ | ★★★★☆ | ★★★★★ | ★★★★☆ |
| GMC Sierra 1500 PU/RC 2WD | ★★★★★ | ★★★★☆ | ★★★★★ | ★★★★☆ |
Fuel cost and engines
About $3400–5000 a year in fuel (EPA estimate). Engines: 3.0L 6-cyl, 4.3L 6-cyl, 5.3L 8-cyl, 6.2L 8-cyl.
In owners' words
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.
2021 GMC Sierra owner · NHTSA complaint 11445068
More owner reports
This is the second time I stop at the grocery store for about 15 or 20 min, get back in the car push the start, then the truck keep cranking with no start for about 20 seconds. Then I try second time and it fires up.
NHTSA complaint 11418942
My truck shakes/shutters at random times. while steadily driving at constant speed and/ or shakes/shutters even more when I try to accelerate.
NHTSA complaint 11460325
Quick answers
Is the 2021 GMC Sierra reliable?
Yes, better than average by government complaints. It drew 1.3× fewer complaints than average filed with NHTSA in its first 3 years, per car sold (Lemon Index 76; 100 is average, lower is better). The best GMC Sierra year by this measure is 2010.
What are the most common 2021 GMC Sierra problems?
In owner complaints to the government, the parts named most are engine (34%), electrical (23%) and transmission & drivetrain (13%). That is the share of complaints, not the share of cars that break.
How many recalls does the 2021 GMC Sierra have?
7 safety recalls (latest: transmission & drivetrain). Recall repairs are free at any dealer; check a specific car's VIN at nhtsa.gov/recalls.
What gas mileage does the 2021 GMC Sierra get?
16 to 26 mpg combined, depending on the engine (EPA estimate).
Is the 2021 GMC Sierra safe?
NHTSA gave it 5 out of 5 stars overall in its best tested version. Ratings differ by body style, and the full table is on the advanced page.
At what mileage do 2021 GMC Sierra problems start?
Half of the owners who gave a mileage reported the problem between 23,900 and 81,000 miles. The middle report was at 51,200 miles, from 141 complaints.
Does the 2021 GMC Sierra have transmission problems?
Transmission and drivetrain issues make up 13% of its owner complaints.
How much does the 2021 GMC Sierra cost in fuel a year?
About $3400 to $5000 a year, by the EPA's current estimate.
What engines does the 2021 GMC Sierra have?
3.0L 6-cyl, 4.3L 6-cyl, 5.3L 8-cyl, 6.2L 8-cyl.
What GMC Sierra year is better than the 2021?
By owner complaints per car sold, the best recent years are 2010, 2012 and 2013.
Lemon Index = safety complaints filed with the U.S. government (NHTSA) in a car's first 3 years, per car sold, against the average car of the same model year. 100 is average; lower is better. A complaint is an owner's report, not a confirmed defect. How it works