Which parts fail
Components named in complaints (battery, alternator, wiring, ignition, instrument cluster, infotainment).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2021 Hyundai Sonata Hybrid owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2021 Hyundai Sonata Hybrid. The contact stated that the key fob was inoperable and after using the key to manually open the door. The contact stated that the vehicle failed to start while pressing the START/STOP button. The vehicle was towed to the local dealer, but the cause of the failure was not determined. The contact was advised that when the failure occurred, to start the vehicle, the battery reset button should be pressed before pressing the START/STOP button. The manufacturer was not contacted regarding the failure. The failure mileage was 24,000.
On Wednesday, October 6th, I was driving full speed (65mph) on a major highway. Multiple lights on the dashboard came on. The LCD display screen for music, apps, etc. went black. More lights came on and others went off on the dash display. I let off the accelerator and steered the car. The fuel efficiency was wilding jumping back and forth. Soon enough, all the lights went back off, but the mileage gauge (fuel efficiency) continued to jump wildly. The brakes seemed to respond differently- almost as if there was a delay between me pressing the brake and the brakes catching. When I needed to accelerate, the car seemed to be having trouble switching between the electric and gas motors. I was able to drive to a safe location and shut the car off. This was terrifying, as the car's computer system or electrical system clearly failed, even if temporarily. …
When the vehicle is turned off the 12v Lithium battery will die. This is a intermittent occurrence that has happened approximately 7 times since [redacted]. Today is December 12, 2024. The car is currently at All Start Hyundai dealership in Pittsburg, CA. This dealership initially denied the car had a problem because they could not duplicate it in a 24 hour period and told me "the car is operating as designed". When I insisted they check the health of the battery, the service department would not do this until they received technical advise from Hyundai headquarters (HQ). It is a multistep process to get to the battery and requires removing the back seat. When HQ advised the battery check, the service department found the battery was swollen and needs to be replaced. I have found information on chat boards and YouTube where other car owners having the same issue. …
What component or system failed or malfunctioned, and is it available for inspection upon request? RANDOM TOTAL ELECTRICAL FAILURE (DOORS WON'T UNLOCK, CAR UNRESPONSIVE) How was your safety or the safety of others put at risk? DIFFICULT TO GAIN MANUAL ENTRY TO CAR, PARTICULARLY IN DARK SITUATIONS Has the problem been reproduced or confirmed by a dealer or independent service center? NO, I HAVE TAKEN THE CAR IN FOR SERVICE TWICE AND THE ISSUE HAS NOT BEEN CORRECTED. THE CAR IS BACK AT THE DEALERSHIP NOW FOR A THIRD ATTEMPT. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives or others? YES Were there any warning lamps, messages or other symptoms of the problem prior to the failure, and when did they first appear? …
I purchased this vehicle pre-owned approximately two years ago and have since developed concerns about its reliability, particularly related to the electrical and hybrid systems. In hindsight, I suspect these issues may be part of the reason the original owner traded it in to a CarMax dealer. Shortly after purchasing the vehicle, I began experiencing recurring problems with the 12V battery, including frequent instances requiring battery resets. Interestingly, these issues were significantly less frequent during colder weather. More recently, as temperatures have increased, the problem has worsened considerably. For about the past month, the vehicle loses power and dies immediately after each drive once the ignition is turned off. This situation escalated yesterday when the "Check Hybrid System" warning light signalled while I was driving on a busy road. …
The vehicle has been turning completely off after use for over a year now. At first it would happen every now and then at the beginning and all you'd have to do was restart the car manually. Now every time the car is turned off it needs to be restarted manually now. The car will also shut itself off while you are driving. It will tell you something is wrong and then won't let you get over 15-20 MPH. If you are on a neighborhood, it's less dangerous for this to happen where you can pull over and turn off the car and restart it. But I have seen other post that they've started to malfunction on the freeway and highways before. My car is a 2021, but recently I've seen 2023 models are doing this as well. I know some people on the internet have gotten their car fixed by replacing a back logged battery. …
The vehicle experiences sudden, complete electrical power loss while driving at speed on highways and city streets or on the parking. All digital displays turn off, the engine shuts down, and power-assisted steering and braking are instantly lost without prior warning, presenting an extreme collision risk. The issue first occurred in August 2025 at approximately 48,000 miles and was taken to an authorized Hyundai dealer in Michigan for warranty repair. The dealer held the vehicle for over 30 days but failed to correct the defect. The identical power failure has continued and recently escalated to daily occurrences. A second Hyundai dealer (Pacifico Hyundai, Philadelphia, PA) diagnosed an intermittent open circuit in the engine wiring harness but Hyundai Motor America refuses to repair the vehicle under warranty, claiming 'outside influence' without providing evidence. …
This is on my 2021 Hyundai Sonata Hybrid Limited - for the 7th time the vehicle has been completely dead and unresponsive. I have had to gain entry to the vehicle using the manual key and press the "jump" button to get the vehicle to start. The Hyundai dealership ran a bunch of battery updates to the 12 volt battery several weeks ago and said that should hopefully fix the issue. Several weeks later on 07/19/2025 the vehicle was dead again. I had to use the key to manually gain entry and jump the car again. The dealership said that the 12 volt battery may need to be replaced and said that it is fully integrated with the hybrid battery system which is covered for 10 years/100K miles whichever comes first. I am still within the warranty period so hopefully Hyundai will fix the issue. From an online search, it appears this is not an uncommon issue with the Hyundai Sonata Hybrid. …
The BMS module within my cars hybrid system failed causing a parasitic drain on the hybrid battery. The dealership where the work was performed would have to be contacted for pictures. The hybrid battery system swole to a dangerously inflated level and did not produce any codes for an OBD reader to pickup. This has caused the dealership to turn my car away multiple times before finally performing the in depth inspecting required to verify battery swelling. This is a known problem throughout the internet I searched "2021 hyundai sonata hybrid battery dying every day" reddit has plenty of user with the same issues. I am not aware of who has inspected my battery besides the dealership. There was no warnings at all the only reason my battery was finally looked at is because of my persistence.
the car keeps randomly dying (not during driving "yet") it happens at least once or twice a week of where i go to ride my car and it is completely dead, i have to unlock the door using the key fob manually and push the "Reset 12v battery button" inside the car. i have tried to have Hyundai service repair the issue or at least tell me what's wrong but no hope as they can never replicate the problem. I am seeing alot of users posting online on numerous web forms (reddit,facebook..etc) that they are having the same exact issue as me for the same exact model of my car, With also no help from the dealer on the matter. This must be a defect at some point and would greatly appreciate if NHTSA can help push this issue to the dealer
NHTSA investigations
Pedestrian alert sounds
NHTSA received a petition on or about July 18, 2022, requesting that Federal Motor Vehicle Safety Standard (FMVSS) 141 be applied to all electric and hybrid vehicles operating in the United States. The petition can be reviewed at NHTSA.gov under ODI Number 11486072. FMVSS 141 establishes performance requirements for pedestrian alert sounds for motor vehicles.
Electrical complaints in other Sonata Hybrid years
Frequently asked questions
How common are electrical problems on the 2021 Hyundai Sonata Hybrid?
NHTSA has 25 complaints about the electrical system of the 2021 Hyundai Sonata Hybrid, 45% of the model year's 55 complaints. The component named most often is 12v/24v/48v battery (1 mentions).
Is there a recall for 2021 Hyundai Sonata Hybrid electrical problems?
No. NHTSA lists no electrical system recall for the 2021 Hyundai Sonata Hybrid. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2021 Hyundai Sonata Hybrid electrical problems start?
Half of the complaints with a recorded mileage happened before about 24,000 miles, and 100% before 25,000 miles.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.