2017 HYUNDAI SONATA Complaints

The Hybrid Electric Vehicle (HEV) system in my 2017 Hyundai Sonata Hybrid Limited malfunctioned. On three separate occasions, the HEV warning light illuminated while I was driving on the highway, followed by a sudden loss of power. The vehicle stalled and stopped running, leaving it inoperable. The incidents occurred in approximately August 2022, November 2023, and February 2026. The vehicle is available for inspection upon request. Each incident occurred while driving on a highway. The vehicle suddenly lost power and stalled in moving traffic, creating a significant safety hazard. I was forced to attempt to move the vehicle out of active traffic lanes while other vehicles were traveling at highway speeds. The unexpected loss of propulsion increased the risk of a crash, serious injury, or death to myself, my passengers, and other motorists. The vehicle was taken to a Hyundai dealership after each incident. However, the dealership did not provide an explanation for the HEV warning light, loss of power, or stalling condition. To my knowledge, no permanent repair was identified, and the problem recurred on multiple occasions. The vehicle was inspected by a Hyundai dealership following each towing event. The vehicle was towed after each incident because it was not safe to drive. To my knowledge, Hyundai did not provide a definitive cause for the failures. The vehicle has not been inspected by police or insurance representatives in connection with

[XXX] [XXX] [XXX]; [XXX] [XXX] [XXX] Date: XXX To: National Highway Traffic Safety Administration Office of Defects Investigation (ODI) Subject: Formal Safety Defect Complaint – 2017 Hyundai Sonata Theta II Engine Failure, Excessive Oil Consumption, Intake/Engine Component Failure and Safety Hazard Dear Sir or Madam: I am submitting this formal complaint and request for immediate investigation into the dangerous and ongoing mechanical failures involving my 2017 Hyundai Sonata equipped with the Theta II engine. I believe this vehicle contains a serious manufacturing and/or engineering defect that presents a substantial safety hazard to consumers. My vehicle has experienced a pattern of progressive mechanical failure beginning with abnormal and excessive oil consumption, which appears to be directly associated with malfunctioning engine airflow and intake-related components. Specifically, the lower engine airflow system and intake functionality appear defective, placing excessive strain on the intake manifold system and contributing to cascading engine failures. As a result of these failures, the vehicle has experienced: Severe and excessive oil burning/consumption Intake manifold malfunction and abnormal operating stress Suspected overheating and/or premature head gasket failure Ignition coil failure and electrical shorting/misfires Progressive engine deterioration rendering the vehicle unsafe and unreliable Increased risk of sudden engine shutdown, stalling, fire hazard, or catastrophic engine failure while operating The vehicle has become increasingly unreliable and inoperable due to these conditions. These failures raise significant concerns regarding public safety, especially given the known history of complaints and recalls associated with Hyundai Theta II engine defects. I am deeply concerned that this vehicle may reflect a broader pattern of defective manufacturing, insufficient quality control. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Supplemental Information to Existing NHTSA Complaint involving a 2017 Hyundai Sonata Plug-in Hybrid (VIN: [XXX] ) While traveling at approximately 70 MPH on a heavily traveled highway, the vehicle suddenly and completely lost propulsion without warning. The vehicle rapidly decelerated in traffic, creating a significant safety hazard for my family and surrounding motorists and requiring emergency maneuvering to reach the shoulder. The vehicle was towed to an authorized Hyundai dealership, where diagnostic testing identified multiple high-voltage battery system fault codes: • P0B68 • P0B6D • P0B72 The dealership diagnosed a high-voltage battery system failure requiring battery replacement. The vehicle is currently non-drivable. During my research, I found multiple owner reports involving Hyundai Sonata Hybrid and Plug-in Hybrid vehicles experiencing loss of power, hybrid system failures, limp mode conditions, and propulsion-related incidents. I also learned that Hyundai previously issued Recall 18V166000 involving 2016–2018 Sonata Plug-in Hybrid vehicles due to battery management system and voltage protection device concerns that could result in loss of power while driving. Dealer says does appply for my car. Although my vehicle’s fault codes may differ from those addressed in the recall, both involve battery-related failures capable of affecting propulsion and creating a highway safety risk. My concern extends beyond my individual vehicle. A high-voltage battery or battery management system failure that can cause a complete loss of propulsion at highway speed without warning presents a potentially serious safety risk. I respectfully request that NHTSA evaluate whether similar incidents involving Hyundai Sonata Hybrid and Plug-in Hybrid vehicles indicate a broader safety concern warranting further review. I can provide dealership diagnostic reports, repair estimates, towing records, photos, and videos upon request. Thank you for your consideration, [XXX] INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATI

I am writing to report a serious, premature failure of a primary emissions and safety-related component (the catalytic converter) that has occurred as a direct consequence of a known, unaddressed manufacturing defect in Hyundai's Theta II engine. My vehicle has a documented history of excessive engine oil consumption. This inherent manufacturing flaw causes the engine to burn motor oil at an extreme rate, forcing unburned oil directly into the exhaust system. Over time, this oil has fouled and destroyed the catalytic converter substrate, triggering trouble code P0420 and causing a complete component failure. A dealership inspection at Heritage Hyundai Towson (RO #XXX) confirmed "excessive wear" and failure of the catalytic converter. Because the catalytic converter is failing prematurely due to a liquid defect (excessive oil burning) rather than standard wear and tear, it poses an environmental hazard, compromises vehicle emissions control, and can lead to sudden engine stalling or reduced power while driving, presenting an active safety risk. Hyundai Motor America (Case #XXX) has formally denied assistance to rectify this consequential damage, despite full awareness of the underlying engine defect. I request that NHTSA investigate how Hyundai’s ongoing oil consumption manufacturing issues are causing cascading safety and emissions component failures in these vehicles. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The rod bearings failed in the engine. The vehicle is currently at the dealership and is available for inspection. Rod bearing failure can cause complete engine seizure while driving, creating a serious risk of losing vehicle control at any speed. This is a known issue with Hyundai's Theta II engine. Yes. The dealership performed a diagnostic on April 27, 2025 and confirmed rod bearing failure. Yes. The dealership inspected the vehicle and Hyundai corporate opened a warranty case and arranged the repair appointment, initially confirming coverage before later denying the claim without providing documentation. The dealership has also repeatedly failed to provide documentation supporting the denial of my warranty claim despite my requests beginning April 29, 2025. I have also been unable to get callbacks from the dealership after being promised updates on May 1st, May 7th, and after requesting a manager on May 18th. As of May 27, 2025 I have still not received any documentation or a callback. The check engine light came on prior to the failure. I proactively checked and changed the oil, added Lucas oil treatment, replaced the spark plugs, and replaced the battery attempting to diagnose and resolve the issue before bringing it to the dealership. No oil pressure warning light ever appeared. The check engine light persisted despite these efforts which is what led me to bring the vehicle in.

I have a Hyundai Sonata 2017 one year after I bought the car I started having acceleration problems. I have had the throttle changed and the valve gasket cover repaired. On April 15, 2026 the check engine light came on. On April 29th I got theta 2 emissions update installed at Hyundai Auburn, Al. I took it too auto zone the same day the code P1326 was showing up and P0014. On May 5th my car entered limp mode for excessive oil leakage, I got an oil change April 6, 2026. My car has never done that until the update was installed. I get my oil changed every 6 months and also have sent them records. They denied my claim due to lack of maintenance.

Engine failed while driving, Took it to dealership and the engine is seized. We were declined by Hyundai an engine replacement even though the Theta 2 engines have a lifetime replacement warranty because these engines are known to fail. They constantly deny due to 'severe owner neglect' because people do their own oil changes.

The vehicle experienced repeated engine-related failures associated with the P1326 error code, which indicates a potential engine defect. The issue first occurred around February 2023 at approximately 51,500 miles, when a warning light appeared. The problem has recurred multiple times despite inspections and service attempts. In January 2024, a dealership performed a software update related to the P1326 code. Shortly after this update, the engine began consuming excessive oil (approximately 2 liters per 1,000 miles). The condition worsened over time, and the vehicle failed an oil consumption test conducted by a dealership. The issue was confirmed by an authorized dealership, which ultimately diagnosed the engine as failed and requiring replacement in May 2026 at approximately 99,000 miles. The problem has been reproducible, with the P1326 warning code appearing multiple times over the life of the vehicle. This condition creates a significant safety risk because the engine may lose power, misfire, or stall unexpectedly while driving, increasing the risk of a crash, especially at highway speeds or in traffic. The vehicle has already experienced engine misfire and severe performance issues. Warning indicators included the P1326 error code and check engine light, which first appeared in 2023 and recurred multiple times thereafter. The engine oil consumption issue developed after the 2024 service and continued to worsen. The failed engine is currently available for inspection upon request.

On 12/20/25, the car - a Sonata plug-in hybrid - failed to start. When I pushed the "start" button, the dashboard display lit up w many clearly irrelevant error messages. Each time I pressed start, somewhat fewer error messages blasted toward me, and finally, no response at all. On 12/21/2026, the tow driver said it was the 12-volt battery. He gave us a jump start and we drove a few blocks. However, it failed at the turn lane while waiting for the light to turn. We turned it back on, bought a new battery, had it installed. On 12/29/25, my husband was driving. He turned into the intersection with a traffic light. As he was making the turn, the car simply quit. No warning. The car was dead, and blocking traffic! He pressed the start button to turn off the car, then again to turn it on. He was able to complete the turn and parked on the side of the road. By this time it had a "check engine" light on. He then drove slowly the few blocks back to our house. On 12/30/2025, the car was towed to a local mechanic. He said it threw the code PODE7, "almost certainly for a failed High Voltage battery." It was still under warranty, and we had the car towed to the dealership. After keeping it for 2 or 3 weeks, they confirmed the code and that the control panel needed to be replaced. We finally picked up the car (w new control panel) on 2/20/2026. In the meanwhile, we looked up Hyundai control panel repairs on a reddit forum. We found lots of chatter about it. Turns out it's a recognized problem in Sonata and Ioniq EV and PHEV's! Clearly, a car failing in the middle of an intersection, highway, etc is a safety problem and needs to have repair/replacements made BEFORE THEY HAPPEN!

Engine experienced severe metallic knocking and loss of power. A certified Hyundai technician confirmed a FAILED Bearing Clearance Test (RO #354331). Hyundai Motor America is refusing to honor the Engine II Class Action Settlement warranty, citing internal code A99 because the vehicle was purchased at an auction, even though the title is CLEAN. This pose a safety risk of engine seizure and potential fire.