2021 HYUNDAI SONATA HYBRID

Owned car since 09/2024 with 64K miles. Battery system (12V/hybrid system) has shut down and died 47 times since 04/2025 - no shut downs before then. Car with ~69K miles at that time. Dealer had car six weeks (05/17 to 07/05/2025) and it died “a number” of times and report that Hyundai claims this is “what the car is supposed to do.” Since 07/05 it has died 12 times just sitting in my driveway or the lot at work. This is NOT normal. Internet blogs show DOZENS of other Hyundai hybrid owners reporting the exact same issue. Car now with 75K miles and under warranty. Dealer will not replace battery system.

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. I am waiting on Hyundai for a fix and for .

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? NO As a reference: [XXX] Key Takeaways from the Thread: Several 2021 Hyundai Sonata Hybrid owners (and a few Ioniq and Elantra Hybrid owners) are reporting the exact same symptoms: Random total electrical failure (doors won’t

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.

12v battery dying randomly

Air flow check engine light alerted and source was faulty fuel injector which required replacement of 4 fuel injectors.

Overheated engine alarm came on while I was on the freeway on a rainy day. Vehicle was towed to Hyundai dealership in which service technician found that the part preventing water from leaking into the muffler was broken. Hyundai dealership has ordered replacement part but it is on backorder. The broken part that needed replacement has been on backorder for close to a month and there is not an ETA of when the part will be received. Prior to the overheated engine alarm going off, cold air was blowing out of the vents even when the heat option was selected.

Coolant system leaks in to the engine or exhaust system, which is evident in white smoke exhaust and coolant level dropping. In my situation, I required an entire container of coolant to perform a daily commute, and the reservoir was empty by the time I made it to the dealership. Car is rendered undrivable due lack of coolant and engine overheating. My car was in the dealership repair facility for 6 weeks awaiting parts on back order due to nationwide shortage. A technical service bulletin has been issued for this manufacturer defect (23-EM-009H). Cost of repairs was roughly $2,300.

My 2021 Hyundai Sonata Hybrid seems to be leaking coolant into the exhaust system. Various reports online indicate that this is a consistent issue with 2020-2022 Hyundai Sonata Hybrid models. A lot of the reports indicate that owners have tried getting theirs cars repaired for the same issue I have a various dealerships all across the US, but either haven't had any luck or have had a temporary fix for the issue, which proceeded to occur again every couple of months. I personally have had my car inspected by my personal dealership and they have confirmed the issue and have mentioned that other owners have brought theirs in to be checked out, but haven't really had luck. I believe that Hyundai should take responsibility for this and issue a recall on the affected models. I bought the car in good faith hoping for reliability but haven't had it for even 6 months now and this problem is here. For safety or myself and others on the road, this models of the Sonatas need to be recalled and rep

My 2021 Hyundai Sonata Hybrid seems to be leaking coolant into the exhaust system. Various reports online indicate that this is a consistent issue with 2020-2022 Hyundai Sonata Hybrid models. A lot of the reports indicate that owners have tried getting theirs cars repaired for the same issue I have a various dealerships all across the US, but either haven't had any luck or have had a temporary fix for the issue, which proceeded to occur again every couple of months. I personally have had my car inspected by my personal dealership and they have confirmed the issue and have mentioned that other owners have brought theirs in to be checked out, but haven't really had luck. I believe that Hyundai should take responsibility for this and issue a recall on the affected models. I bought the car in good faith hoping for reliability but haven't had it for even 6 months now and this problem is here. For safety or myself and others on the road, this models of the Sonatas need to be recalled and rep

EHRS Coolant Leak- problem started in [XXX] when engine overheated. The weather in Michigan in inclement and being stranded in the intense cold can lead to loss of life. I had it towed to a Hyundai dealership that was unable to find the problem and in attempting to "find a leak" used the incorrect dye, necessitation transferal to another more competent dealership where the problem was diagnosed and was fixed with a replacement part. In December 2023 a TSB 23-EM-009h was issued by Hyundai describing this problem and issuing a part (Center Muffler). I was not informed and the problem recurred. currently this is the third episode and Hyundai after paying 95% of the previous cost, now only agrees to pay 85% and denies reimbursing me for the car rental. Warning lights appeared with all 3 occurrences. Hyundai should have issued a recall to obviate this. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

the car randomly goes into dead or limp mode and unable to start. need to jump start it to come alive. No codes shown once its jumstarted. it has happened at random on several occasions.

When the vehicle is turned off the 12v Lithium battery will die. This is a intermittent occurrence that has happened approximately 7 times since [XXX]. 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. Why hasn't Hyundai HQ issued a recall and replaced all the batteries? The dealership has told me there are batteries in inv

On three separate occasions, while going very fast (60-78 mph), the automatic emergency braking system turns on. The warning lights flash and there is some type of warning noise. I don't even know if it starts to break because it scares me so much, I just press the gas. It turns off within a couple of seconds, but that is not the point. If I didn't react so fast, I am unsure of what could actually happen.

On three separate occasions, while going very fast (60-78 mph), the automatic emergency braking system turns on. The warning lights flash and there is some type of warning noise. I don't even know if it starts to break because it scares me so much, I just press the gas. It turns off within a couple of seconds, but that is not the point. If I didn't react so fast, I am unsure of what could actually happen.

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 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.

Mileage: 24,000

On three separate occasions over the last two months, while driving, an alert comes on that says check hybrid system then the vehicle powers off. When this happens, you lose the ability to accelerate break steer, and I have been lucky each of those three times and that I was in a situation where there was not much traffic. I am not able to drive the vehicle at this time. I have reported the problem to Hyundai and they want me to drive the vehicle to the dealership for another check of it. They have looked at it once before and have not been able to diagnose a problem. It is unsafe to drive and they are not willing to assist in getting the vehicle to the dealership without me getting it over there.

On three separate occasions over the last two months, while driving, an alert comes on that says check hybrid system then the vehicle powers off. When this happens, you lose the ability to accelerate break steer, and I have been lucky each of those three times and that I was in a situation where there was not much traffic. I am not able to drive the vehicle at this time. I have reported the problem to Hyundai and they want me to drive the vehicle to the dealership for another check of it. They have looked at it once before and have not been able to diagnose a problem. It is unsafe to drive and they are not willing to assist in getting the vehicle to the dealership without me getting it over there.

Coolant leak acting like blown head gasket. Coolant was leaking into the exhaust system. Defective EHRS system