Driving 70 mph, warning lights and alarms "Hybrid System Failure" "Vehicle shutting down" and then it does. No lights, no hazards, no power. Push button battery restart starts it again with no visible issues. Driving 30 mph, warning lights and alarms "Hybrid System Failure" "Vehicle shutting down" and then it does. No lights, no hazards, no power. Push button battery restart starts it again with no visible issues. Driving 58 mph warning lights and alarms "Hybrid System Failure" "Vehicle shutting down" and then it does. No lights, no hazards, no power. Push button battery restart starts it again with no visible issues. ^This is an ongoing issue. It's also been powerless several times while parked.

- Pomaria, SC, USA

My car will power off randomly, or will seem as though there is no power. I have to revert back to the manual key to enter the vehicle and hit the 12vlt reset to power it back on. This happened at least 3 times. Once while operating the vehicle, and twice while the vehicle was left parked. This is not a low battery issue as, the car will only do this occasionally, and not every time I enter and turn on the vehicle. There is no error code to follow this mishap as all power goes out and the dealer maintenance has nothing to work with.

- Irving, TX, USA

faulty engine thermostat

- Las Cruces, NM, USA

Initially had loss of cabin heat. Later, vehicle randomly overheated. Repair shop replaced EGR due to finding confidant buildup of water/coolant mix. Within one week, problem returned. Dealer notified me that while replacing another part they found a TSB for coolant leakage into exhaust that was consistent with my issue. After research, it is clear that this is a widespread failure and should be a recall.

- Avon, IN, USA

Hyundai 2021 Sonata Hybrid. Blown head gasket. Reported 1,000 miles after warranty expired. Car was in the shop for Hybrid battery issues. Repair completed. 2 weeks later smoke coming from the exhaust. Hyundai says blown head gasket - will not honor warranty as I was just a few thousand miles over warranty. Seems to be a common problem with the Hyundai not honoring the warranty.

- Timonium, MD, USA

Antifreeze is coming out of the exhaust. Heater is only blowing cold air. Repair shop said it is a common problem with the Hyundai hybrids. Was told I had to take it back to the dealership. The y repair shop said this is very common and is wondering why a recall has not been issued by the NTHSB. Dealership has been unresponsive.

- Timonium, MD, USA

My vehicle's heat stopped working suddenly. A short while later, I received and overheat warning for the engine. I had to stop repeatedly on the shoulder of the highway to allow the car to cool so I could move it to a safe space at the next exit. The dealer has confirmed that the coolant was leaking into the exhaust system and burning up. This resulted in white smoke, inconsistent power, and a stumbling engine when it would switch over from the electric to the gas engine. This problem comes on suddenly and can leave you in a very bad situation since there is no warning to this problem. The dealer reported my car had no coolant left in it which is why it was frequently overheating. I have read about this problem on many online forums and it seems to be very common in this car. Hyundai needs to create a fix.

- Limerick, PA, USA

I was on the highway going 60 mph then all of a sudden my vehicles rpm's jumped way up to 8 and completely lost power was on I-45 in Conroe thankfully I was in the slow lane. I have attached pictures of my dash so I could get proof this time. I had to wait 7 minutes for the car to do anything. It also burned all of my engine oil. So had to buy oil for my vehicle. I just had my oil change 3 weeks ago. This has happened before on on the frontage road a few months ago. I have claims open with Hyundai Customer Care. I have been stating that my engine makes a clicking noise, it hesitates, and seizes all the time. I have had this problem since March of 2021 and I bought the car in January 2021. I know I am not a part of the engine recall but I should be. I am scared to drive it. Hyundai doesn't care one bit. Well enough is enough I will be getting rid of this death trap. If you are looking at Hyundai's don't waste your time or money.

- Conroe, TX, USA

While driving, engine alerted that it was overheating. Pulled over and coolant was very low, so I refilled it and then while driving to my family's garage to use the lift, saw white exhaust smoke. Took it to an independent mechanic, and in the ~10 mile trip there, over a quart of coolant had been burned off. He was able to reproduce the issue. No issues with the engine operation, it runs well and efficient, no check engine light. Mechanic found that a coolant line runs to the middle of the exhaust system and that this seems to be the issue. Other owners seem to have reported this same issue with this same model and roughly the same year, in which the muffler assembly needs replaced due to coolant leaking into the exhaust. Only prior issue was less warm air out of the vents for the previous week or so, but no other issues or warnings.

- Columbus, OH, USA

the coolant reservoir has been dropping showing levels below min even after topping it off

- Woodbury, MN, USA

I have a 2021 Hyundai Sonata SEL with a Smartstream 2.5L engine w/ GDI & MPI. I have have always heard a loud knocking noise coming from my engine since I got the vehicle when in park. When you are accelerating it hesitates and you can hear a knocking noise. I have taken it to the dealership multiple times and they were able to feel and hear what I was talking about but ensured me it was fine. Recently it has been a lot worse. On 10/18/2023 I was getting on to the highway from the feeder. I tried to accelerate to about 50 mph and I heard the same knocking noise and my rpms jumped all the way to the top. Then my car suddenly stopped getting on to the highway. It took it about a minute before I could start driving again. Luckily there was no one behind me because it could've been really bad. I got home and looked under the hood and it looked like oil had sprayed out of the engine. You could to see oil splatter on the fender. No one was hurt thankfully. I have been complaining about the knocking and hesitation while accelerating for almost 2yrs.

- Conroe, TX, USA

Discovered that I had no engine heat to use in the cabin with cooler outside temps. Checked coolant tank. Was nearly bone dry. 2021 hybrid is under warranty with only 35K miles on it and regular scheduled maintenance. Have also noticed puffs of white smoke upon easy acceleration and switching from battery to gas. Refilled engine coolant, but it continues to leak internally with use (no evidence of pooling under car) with short mile trips. Had to leave at dealership for repairs and cannot get a repair date for another month out. Other hybrid owners of 2020 and 2021 report their dealerships discovered the coolant is leaking into the engine and mixing with the exhaust (thus the white smoke). I am adding my car to the list of others who have reported the same problem.

- Christiansburg, VA, USA

The contact owns a 2021 Hyundai Sonata. The contact stated while driving 45 MPH, the vehicle inadvertently lost motive power in the middle of the roadway and failed to restart. The vehicle was pushed to the shoulder of the roadway, where the failure persisted. No warning lights were illuminated. The vehicle was towed to the dealer, who determined that there was no oil in the engine, causing the engine to seize. The vehicle was then towed to another dealer, who confirmed the diagnostic results. The contact stated that an oil change was performed three days prior to the failure. The vehicle was not repaired. The manufacturer was notified of the failure, and a case was opened. The failure mileage was 44,000.

- Saint Johns, FL, USA

This car is a Hybrid The car has a 12V battery reset system which stops the 12V battery from draining to zero voltage. This is a design feature. However, since purchasing this car we have had Hybrid Engine Failure warnings happen 3 times, in 2 months. When this happens the car engine shuts down, no matter at what speed you are driving! The car gives a warning on the dashboard that states - Hybrid System Failure - and the engine shuts down. The dashboard goes completely bland as all electronics are switched off. This has happened 3 times, 2 of them occurred on the freeway at high speed. Luckily we were able to pull over without being impacted by another vehicle. After a few seconds of stopping we are able to push the 12V Battery reset switch and the engine restarts when the start button is depressed. After the first incident the car was given to the local Hyundai dealer and they found nothing wrong with the car. It has happened twice since the car was returned to us and the car is currently in the Hyundai dealership, a different one, for diagnosis. We do not want to drive this car until the fault is determined and corrected

- Mesa, AZ, USA

The issue is well known across the DN8 platform, hundreds if not thousands of people have this problem.Car and driver even did an article on a car with this same 2.5L turbo DCT engine having the same problem! The problem is the ITMS or thermostat housing unit. I first experienced this getting on to a highway, I lost all acceleration, the turbo dropped to 0 pSI and I received an engine overheating warning on the dash. After pulling over the car resumed normal driving, but with oil temps running 30-40 degrees higher than normal. Since then, I have had loss of boost and acceleration when passing around cars which has almost caused accidents, oil temps constantly running very high and fans constantly running on full blast even after car is off. I have been to the service center 4 times, and they have failed to "replicate" the issue and stated the fan and oil problem is "normal" which it is not. This problem needs to be addressed before somebody gets seriously hurt due to loss of power unexpectedly while driving. PLEASE help! Thank you for your time.

- Norfolk, VA, USA

When attempting to pass other vehicles or under quick acceleration such as an on ramp to the highway, the vehicle will experience a sudden loss of power and oil pressure resulting in a fail safe mode which limits your acceleration and causes a sudden decrease in speed and velocity. The issue results in the oil pressure light illuminating and requires the vehicle to be stopped and completely turned off to reset then once turned back on, the problem is -??gone-?? until a sudden acceleration occurs again, which results in the same issue happening. There is a current recall out for similar models but my vin is not listed. I have approximately 50k miles on the car, and am the first owner.

- Clarksville, TN, USA

When I arrived in the parking lot and selected the R (reverse), the vehicle stayed in the D (Drive) although that it was moving backwards and was able to park it. The shift selector was stuck in DRIVE (Drive) leaving the vehicle on but not operational. After several attempts to allow the vehicle to cool and the battery to reset, (30 minutes_ later), the car started and took the vehicle to be serviced. The vehicle technician said they had a difficult time diagnosing the vehicle because it was giving different codes. They said that while testing they found the Transmission Shift Selector Module was damaged. Not physically but electronically damaged. They also stated that the car could have other problems but that they needed to replace the module first because it could be the cause of the other errors.

- Arlington, VA, USA

The cabin heater started blowing cold air in February. One shop said the car was low on coolant and topped it off. I made an appointment to take the car to a dealer because it's still under warranty (<37k miles). I had to wait 3 weeks. A few days before my appointment, the cabin heater started blowing cold air, again. There is no indicator that the coolant is low. The engine temperature is one of a dozen gauges one can scroll thru, but the "engine overheating" warning started flashing before I thought to check the temperature guage. Smoke came out of the exhaust and, once stopped, from under the hood. There was a risk of an engine fire and/or permanent damage to the engine.

- Evanston, IL, USA

My 2021 Sonata has 32,000 miles & it broke down in the middle of the road. My safety & my daughters safety were at risk. We could have been hit or killed. There were no warning lights. It had to be towed. Repair shop reports the transmission is no good. This vehicle should not have transmission issues. Hyundai will not even cover a rental car. The dealership can-??t even work on it for 1-2 weeks. I work & have kids. I need a vehicle. The car breaking down in the middle of the road with no warning is dangerous.

- Georgetown, DE, USA

Very loud car alarms sounded, e.g., it sounded like a something like a red alert in an old Star Trek episode. warning light indicated engine overheated, extreme exhaust/smoke bellowed out from rear of car while decelerating on highway exit ramp. My wife and I were inside the car during this event. This event happened on 5 pm EST December 9 at Hamilton Avenue exit on Ohio 126 Cross County Highway (Ronald Reagan Highway) in the Cincinnati metropolitan area. Had to park car within one mile. I had the car towed to the nearest dealer after it had cooled for 1 +hour. I was afraid the engine was going to explode or catch fire as I was decelerating. The dealer suggests the heat exchanger needed replacement. However, after 45 days, Hyundai has not shipped the heat exchanger that I have been made aware. I am concerned this event may be likely to reoccur and with resulting potential injuries to the occupants inside.

- Loveland, OH, USA