2015 Hyundai Sonata: sudden loss of power

Filed Nov 9, 2026 · Engine · TX

was driving my 2015 Hyundai sonata with my daughter and there was a really loud thump, like something came apart. there was instant smoke and really loud knocking and reduced power. Right after that, I pulled over into a church so I wasn't blocking traffic, and when I got out, there was oil coming out everywhere and a hole in the engine block. I read about a lawsuit settlement and seeing that alot of drivers get a flashing engine light and car reduce power. That is not what happened with me, was just a loud pop, smoke and loud knocking. This has put me and my daughter at risk. I’m asking the federal safety agency to investigate why an engine with an update that was installed to prevent what happened could fail on the road, produce that much smoke, and spill oil the way it did. I had a driveway to pull into but another driver might not of have nowhere safe to go. If Hyundai knew this type of failure could happen, I want the federal safety agency to look at whether the update gives drivers enough warning and whether more needs to be done to keep these cars safe on the road.

Filed Oct 14, 2026 · Engine, Fuel system · MS

A franchise dealership performed a federally mandated safety recall service (ECM Software Update) and a knock sensor replacement on this 2015 Hyundai Sonata 2.0L Turbo. To perform these specific repairs, the technician had to work directly around the intake and turbocharger assembly workspace. Immediately after picking up the vehicle, it suffered a sudden and dangerous loss of power and refused to accelerate normally on the highway, creating a severe traffic hazard. Upon an immediate emergency inspection by the same service center 5 days later, the dealership documented in writing that the turbocharger intercooler hose clamps were completely off/unfastened. Because the technician left the clamps disconnected, the turbo lost sealed pressure, failed completely, and began dumping high-pressure engine oil backward through the air filter intake box. The service center is now refusing to take responsibility for the mechanical safety failure directly caused by their technician's recall repair negligence.

Filed Aug 10, 2026 · Engine · 88,000 miles · MI

The contact owns a 2015 Hyundai Sonata. The contact stated that while driving on several occasions at various speeds, the vehicle lost power, and the check engine warning light was illuminated. The vehicle was taken to a dealer where it was diagnosed that the engine had failed and needed to be replaced. The vehicle was repaired, but the failure reoccurred within a year. The vehicle was taken back to the same dealer where it was diagnosed and determined that a software update was needed. The vehicle was repaired, but the failure persisted. The vehicle was then taken back to the same dealer, and there was oil on the pistons and a tune-up was needed. The vehicle was repaired, but the failure persisted. The vehicle was taken back to the dealer, where it was advised that an oil consumption test could not be provided until the pistons had failed. The manufacturer was notified of the failure, and a complaint was filed. The failure mileage was approximately 88,000.

Filed Aug 8, 2026 · Engine · FL · fire

Vehicle: 2015 Hyundai Sonata VIN: [XXX] Mileage: ~85,000 Description of the Problem: While driving, the vehicle suddenly began producing thick smoke from under the hood without warning. I safely maneuvered to the shoulder to avoid an accident. The engine subsequently seized completely and became inoperable. My mechanic diagnosed this as a known internal manufacturing defect in the Theta II engine (connecting rod bearing failure), a widely documented issue for this model and production year. Oil and coolant levels were confirmed normal with no leaks, ruling out maintenance neglect. I initially paid for an unnecessary starter replacement before this diagnosis was confirmed. This is a serious safety hazard that could cause loss of engine power and control while driving, posing a risk to myself and other drivers on the road. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed May 1, 2026 · Engine · DE

Engine – connecting rod bearing failure. Theta II engine. Hyundai confirmed the defect via Bearing Clearance Test (BCT) on October 3, 2025. The engine can seize without warning, causing sudden loss of power while driving – a clear safety risk. The problem has been confirmed by an authorized Hyundai dealership (Hertrich Hyundai of New Castle). The manufacturer issued Technical Service Bulletin 22‑EM‑001H (TXXI lifetime warranty) covering this exact defect. Despite confirming the failure, the manufacturer has refused to repair the engine. The vehicle is available for inspection upon request. No crash, fire, or injury occurred. Warning signs included engine noise and illumination of check engine light before failure.

Filed Apr 4, 2026 · Engine · OH

Engine seized driving down the interstate doing 65 MPH in rush hour traffic could have been rear ended or hit vehicles around me trying to get off the road. Complete loss of power. Power steering was still active brakes were barely working. No warning lights (I had the knock sensor recall performed). Engine simply locked up solid. I was able to safely make it to the disabled vehicle lane and put the car in park. Engine had no sludge buildup and looked excellent once it was disassembled by the dealer. All engine bearings had spun. Engine was completely replaced under the extended warrenty.

Filed Mar 3, 2026 · Engine · NJ

Check Engine light is flashing on dashboard. Reduced Vehicle speed. Car will not drive beyond 62 miles.Lost of power during acceleration.

Filed Feb 19, 2026 · Engine · GA

Engine has knocking sound. Sudden loss of power and hesitation when accelerating

Filed Feb 18, 2026 · Engine · PA

The vehicle suddenly lost power while driving on a public roadway. Immediately after, the vehicle began producing a large amount of smoke. The smoke quickly filled the cabin, making it difficult to breathe and creating an urgent safety hazard. My passenger and I had to exit the vehicle right away due to the amount of smoke. We were exposed to smoke inhalation and were stranded on the side of the road in unsafe weather conditions for over an hour while waiting for a tow truck. I later learned that the vehicle had an open recall related to engine issues; however, I was never notified of this recall. Regardless of recall status, the sudden loss of power combined with heavy smoke and potential fire risk created a dangerous situation that could have resulted in serious injury or death. I believe this issue represents a serious safety defect and fire hazard that could endanger other drivers.

Filed Feb 17, 2026 · Engine, Fuel system · SC

Component/System Failed: Engine – connecting rod bearing failure consistent with Hyundai Theta II engine defect subject to federal recalls and Consent Orders. The vehicle previously received Recall Campaign 953 (KSDS software update), intended to detect premature rod bearing wear. The engine is currently knocking and has been diagnosed as requiring replacement. The vehicle and engine are available for inspection upon request. Safety Risk: Rod bearing failure can cause sudden engine seizure or stall while driving, creating a significant crash risk due to loss of power steering and braking assist. Engine failure DID occurr despite prior recall software update, indicating potential recall remedy ineffectiveness. Sudden stalling in traffic placed myself and others at risk of collision. Dealer Confirmation: Hyundai of North Charleston confirmed through warranty history a prior engine replacement request (PA) was submitted by a previous owner but denied. The recall repair was never performed. Current diagnostic findings indicate engine failure consistent with known recall defect. However, Hyundai has refused to perform further inspection or goodwill repair solely due to the vehicle’s salvage branding. Inspection History: The vehicle has been inspected by a Hyundai dealership. No engine replacement was completed. Hyundai Customer Care has updated case notes but is declining remedy based on title status rather than mechanical condition. Warning Lamps/Symptoms: The vehicle previously received KSDS software update. Engine knocking developed consistent with rod bearing wear. The software did not provide effective prevention of engine failure. The engine now requires replacement. Hyundai is refusing recall-related remedy due to salvage title (predates my wonder ship by many years), despite federal recall obligations applying to the vehicle VIN. This complaint concerns potential failure of recall remedy effectiveness and denial of defect-related inspection.

Filed Feb 14, 2026 · Engine · CO

While driving on the freeway, my vehicle experienced a sudden and catastrophic engine failure. The check engine light began flashing, the vehicle lost power, and I almost lost control of the car. I barely had time to pull over to the shoulder to avoid an accident. The vehicle was towed to a Hyundai dealership. The engine does not start and the engine block is cracked. Hyundai denied coverage stating that a software update (Campaign 953) was not installed. Campaign 953 is only a detection update and does not repair or prevent internal engine failure. This is a serious safety issue.

Filed Jan 30, 2026 · Engine · TX

While driving my 2015 Hyundai Sonata, the vehicle suddenly lost power and entered limp mode. A loud engine knocking noise was present, and acceleration was severely limited, creating a safety risk in traffic. The check engine light illuminated at the time of the failure. An independent mechanic confirmed diagnostic trouble code P1326, related to the engine knock sensor detection system designed to detect early engine bearing failure. The condition occurred without warning. The vehicle is currently not being driven to prevent further damage and is available for inspection upon request. Sudden loss of power while driving poses a serious safety hazard. This appears to be a known engine defect affecting similar vehicles.