Short answer: The biggest problems with the 2021 Hyundai Sonata are engine problems, transmission issues, and forward collision avoidance system problems.
Engine problems are the most common while transmission issues and forward collision avoidance system problems aren’t as common.
Some of these problems have even resulted in recalls: Hyundai has issued four for this vehicle.
While most consumers experience reliable ownership when they purchase a new vehicle, some drivers encounter defects that can affect safety or vehicle performance.
In this article, we discuss the most commonly reported problems with the 2021 Hyundai Sonata.
Having Vehicle Problems?
Submit the form below to see if your vehicle qualifies for a lemon law claim.
Common 2021 Hyundai Sonata Problems
2021 Hyundai Sonata Engine Problems
Some 2021 Sonata owners have reported problems involving excessive oil consumption and engine stalling during operation.
Engine Stalling and Oil Overconsumption
- Severity: Moderate to severe; an engine that stalls unexpectedly can leave drivers without power while driving and may create hazardous situations on the road.
- Manufacturer’s Response: Hyundai has issued two recalls involving leaking fuel, which could cause a stall. NHTSA Recall #21V-524 addresses fuel pipe leaks in 2.5L Turbo models. Most recently, NHTSA Recall #25V-796 addresses a defective check valve in 1.6L engines that causes fuel tanks to swell, melt, and leak.
- Fix: Technicians will inspect impacted parts, including the fuel tank and pipe, and replace them if necessary.
2021 Hyundai Sonata Transmission Issues
Some owners of the 2021 Hyundai Sonata reported problems such as delayed shifting, hesitation during acceleration, or sudden jerking when the transmission changes gears.
Rough Shifting, Hesitation, and Sudden Loss of Power
- Severity: High; while rough shifting is an inconvenience, it often precedes a “fail-safe” mode that leaves the driver with only 20–30 seconds to pull over before the car loses all power.
- Manufacturer’s Response: Hyundai has issued NHTSA Recall # 22V-746 for a loss of drive power.
- Fix: Technicians will inspect and replace the transmission as necessary. The transmission control unit software will also be updated.
2021 Hyundai Sonata Forward Collision Avoidance System Problems
Sonata owners frequently report that the Forward Collision-Avoidance Assist system triggers “phantom braking” or displays a “Check Forward Safety System” warning.
False Collision Warnings
- Severity: Moderate; while the car remains drivable, unexpected braking can cause rear-end collisions.
- Manufacturer’s Response: Hyundai has not issued a TSB or recall for this issue.
- Fix: Technicians should inspect and repair or replace any faulty sensors.
2021 Hyundai Sonata Hybrid Battery Issues
A major growing complaint among 2021 Sonata Hybrid owners involves the integrated 12V battery failing or physically swelling.
12V Battery Swelling / Failure to Start
- Severity: Moderate to High; a swollen battery can prevent the vehicle from starting and, in rare cases, poses a chemical or fire hazard if the casing cracks.
- Manufacturer’s Response: Hyundai launched Service Campaign 9B4 to update the Battery Management System software. They also released TSB 23-EE-001H regarding battery diagnoses.
- Fix: Dealers should update the BMS software. If the battery is already swollen, it must be replaced. Owners have reported long part delays for these specialized hybrid components.
Hyundai Sonata Owner Complaints
“Took vehicle in for transmission recall on June 12th. After picking up vehicle the vehicle it was shifting harshly. On the 17th my vehicle had a code come up that said to park it and contact the dealership ASAP. Transmission code P1C2D03. The recall was supposed to prevent this, not cause it.”
“Every day the car is dead, have to take the manual key out pop door cover off unlock car manually push the 12v reset button and hold fob to start/stop button for car to work again. Happens daily.”
“During a front end collision the car did not auto brake and the air bags did not deploy. The car has been totaled and is currently at a dealership for insurance appraisal.”
Defective Cars and Your Legal Options
Lemon laws protect consumers when a vehicle develops substantial defects during the warranty period that are not repaired after a reasonable number of attempts.
When issues affecting safety, reliability, or value continue despite dealership repairs, or when a vehicle spends extended time out of service, the manufacturer may be required to provide compensation, a replacement vehicle, or a refund.
Documentation such as service records and repair invoices often plays an important role in determining whether a vehicle qualifies under lemon law standards.
| Affected Model | Average Lemon Law Settlement |
| 2021 Hyundai Sonata | $50,855 |
*Please note, the figures presented in the chart are approximations based on past case results and should not be interpreted as a prediction or guarantee. Each case is unique and requires personalized legal guidance.
Put an End to the Frustration: Connect with the Experts Today!
If your vehicle has been repaired multiple times for the same problem or has spent a significant amount of time in the dealership for repairs, you may qualify for compensation under your state’s lemon law.
The Lemon Law Experts have helped many drivers attain settlements, replacements, and buybacks for defective vehicles. Call today at (877) 885-5366 or fill out a contact form on our website.
