2016 Hyundai Sonata: sudden loss of power

Filed Sep 15, 2026 · Engine · TX

The vehicle experienced a Theta II engine failure at under 57,830 miles while driving on northbound [XXX] near the [XXX] Parkway U-turn in [XXX]. The engine made a loud noise and lost power. I was able to coast to the far right side of the U-turn under the bridge. I called HERO (Austin's emergency roadside assistance). They responded, determined it was not a battery issue, and pushed the vehicle to the Southern Leisure Spa parking lot on the southbound side of the road. The vehicle was then towed. The vehicle is equipped with the KSDS (Knock Sensor Detection System) software update, installed as part of Hyundai's remedy for this known defect. Despite KSDS being installed, the engine failed due to connecting rod bearing wear, consistent with the documented Theta II defect. A Hyundai dealership confirmed KSDS was installed but denied the warranty claim, citing maintenance records. The vehicle is available for inspection upon request. The Theta II engine defect has been the subject of prior the federal safety agency investigations and Hyundai recalls. This complaint is filed to document another failure of the same defect in a vehicle with the manufacturer's remedy installed. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Aug 25, 2026 · Engine · WA

Component & Inspection: Vehicle engine suffered connecting rod bearing failure and entered restricted P1326 "Limp Home Mode" (max 2,000 RPM). The vehicle is grounded and available for inspection at Bud Clary Hyundai in [XXX].Safety Risk: Sudden, unexpected loss of power occurred while driving, placing me and other drivers at immediate risk on public roads due to the vehicle's inability to maintain normal traffic speed or safely accelerate.Dealer & Corporate Confirmation: Active P1326 engine code is confirmed. Car has been held for 14 days. The franchise is violating federal settlement rules by explicitly refusing to execute the mandatory, free mechanical Bearing Clearance Test (BCT) unless I pay out-of-pocket fees.Inspection & Corporate Compliance Failure: Car was brought to the dealer on XXX. The service manager admitted in writing that they are withholding safety diagnostics to protect shop labor hours due to an automated computer flag regarding a clerical title brand discrepancy. Hyundai Corporate is actively enabling this violation; my case manager refuses to issue a manual compliance override for the safety test and is violating federal settlement terms by withholding my contractually mandated alternative transportation.Warning Lamps & Symptoms: Flashing Check Engine Light and limp home mode triggered instantly and unexpectedly on XXX. There were zero warning symptoms, messages, or abnormal noises prior to that date INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Mar 31, 2026 · Engine · FL

The failure involves the engine, which has seized (locked up) and is available for inspection upon request. The vehicle became unsafe when it stopped operating in traffic, creating a potential hazard to myself and others due to the sudden loss of power and inability to move the vehicle. The issue has been confirmed by both a dealership and an independent service center, both of which determined that the engine has failed and requires repair or replacement. The vehicle has also been inspected by the manufacturer as part of the claim process. There were no prior warning lights, messages, or indicators before the failure occurred.

Filed Mar 17, 2026 · Engine, Fuel system · FL

This complaint is NOT related to the existing recall associated with this vehicle. The vehicle is experiencing a serious loss of power and acceleration issue. The car is unable to accelerate past approximately 60 mph. When pressing the accelerator fully, the vehicle does not respond or increase speed. While attempting to accelerate, the engine RPM increases and then suddenly drops repeatedly, causing the vehicle to struggle to maintain speed. This behavior is consistent and occurs during normal driving conditions. This creates a dangerous situation, especially when merging onto highways or attempting to accelerate in traffic, as the vehicle cannot respond when needed. The issue has occurred multiple times and makes the vehicle unsafe and unreliable to operate.

Filed Feb 11, 2026 · Engine · FL

While driving in normal traffic, the engine experienced a sudden and significant loss of power and went into a reduced-power “limp” mode. The check engine light illuminated and the vehicle stored an active P1326 diagnostic trouble code related to the engine/Knock Sensor Detection System (KSDS). Because this occurred in live traffic, the sudden power loss created an unsafe situation that increased the risk of a collision, as the vehicle could not accelerate or keep pace with surrounding vehicles. This issue appears to be directly related to Hyundai Technical Service Bulletin 22-EM-001H-1, which addresses known engine defects and P1326 activation in this model and engine. The vehicle was taken to a Hyundai dealership in West Palm Beach, Florida for inspection, where the code was verified and documentation (including oil change records) was requested. The vehicle has approximately 89,000–90,000 miles. After the dealership inspection, I received an email from Hyundai Motor America Consumer Affairs [XXX] ) stating: “This is Hyundai’s final position in this matter, and we are unable to offer any assistance with regard to this claim.” I believe this position is incorrect, as the symptoms and P1326 activation align with the conditions outlined in TSB 22-EM-001H-1, which Hyundai is supposed to honor when these failures occur. To my knowledge, the vehicle/component has not been inspected by police or insurance representatives. The check engine light and reduced power symptoms first appeared at the time of the incident. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Feb 1, 2026 · Engine, Fuel system · DE

My 2016 Hyundai Sonata (2.0T/2.4L engine) has been experiencing loss of motive power and severe engine stumbling at stoplights, creating an unreasonable risk of a crash in traffic. The Check Engine light is on with DTC P0010. Upon inspection, the internal oil seal plug at the intake camshaft E-CVVT has become unseated, causing an active oil leak. This matches the exact defect and symptoms (elevated idle of 1,200–1,400 RPM and power reduction) described in Hyundai Service Campaign TX3 (TSB 15-01-022-1). While that campaign only applied to 2015 models, my 2016 vehicle has suffered the identical failure. I am requesting that this safety-related defect be investigated for 2016 models to prevent potential engine fires from oil leaks or accidents from sudden power loss

Filed Jan 19, 2026 · Engine, Fuel system · IL

This vehicle has experienced multiple hybrid system failures while driving, including a complete loss of power “Hybrid System Warning – Turn Engine Off” on the interstate in June 2022 through November 2025. These events have placed me and my loved ones in dangerous driving situations. Despite a warranty‑covered engine replacement at 82,015 miles (January 2023), the same hybrid system issues have recurred. Hyundai initially indicated a warranty claim was submitted, then told me there was no record of any claim in the system. The dealership claims it was denied — creating a serious inconsistency in communication and accountability. In addition, I have identified multiple the federal safety agency complaints in the database from other owners of 2016 Sonata Hybrids (VINs beginning with KMHE) describing similar highway shutdowns and hybrid system failures, which raise concern about a broader, unaddressed safety defect not currently covered by existing TSB or recall actions. I am respectfully requesting: A regional inspection and review of my vehicle prior to any further work. A review of Hyundai’s handling of this warranty claim and the discrepancy between dealer and corporate communication. Assessment of whether the hybrid system failures in KMHE‑prefix Sonata Hybrids warrant further safety action.

Filed Dec 16, 2025 · Engine, Transmission · UT

On November 10, 2025, my 2016 Hyundai Sonata Hybrid (VIN [XXX] , approximately 150,000 miles) experienced a sudden loss of power while I was turning right and accelerating into traffic. The vehicle immediately entered limp mode with flashing warning lights and audible alerts. The vehicle lost normal propulsion and could not accelerate properly, creating a dangerous situation as it was blocking a traffic lane. I was forced to limp the vehicle into a nearby parking lot to get out of traffic. The vehicle was not safely drivable afterward and was towed home. A few days later, the vehicle was towed to Murdoch Hyundai in Lindon, Utah, for diagnosis. The vehicle was found to have diagnostic trouble code P1326, which Hyundai identifies as activation of the Knock Sensor Detection System (KSDS) related to connecting-rod bearing wear. This condition is part of Hyundai’s known engine defect and safety recall/warranty extension programs. During inspection, the dealer observed that the valvetrain did not show signs of neglect or sludge, which is inconsistent with oil starvation or severe maintenance neglect. This further supports that the failure is consistent with the known connecting-rod bearing defect addressed by Hyundai’s KSDS safety recall, rather than a maintenance-related issue. This is a safety issue because sudden loss of propulsion or reduced power while entering traffic creates a high risk of collision. Hyundai customer care has been unwilling to open a new case number or escalate review, and the dealer has indicated possible denial of engine replacement coverage based on incomplete oil-change records, despite the vehicle exhibiting the KSDS safety condition. I am requesting the federal safety agency review of this safety-related defect and the manufacturer’s handling of KSDS/P1326 failures. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Nov 17, 2025 · Electrical, Engine · OH

The vehicle experienced an engine and power train failure while driving on the highway, resulting in sudden loss of power. The electrical system also failed after the dealer visit, causing the battery to die every morning. Yes, the vehicle is available for inspection upon request. My car suddenly lost power on the highway and would not accelerate, forcing me to pull over on the shoulder with traffic moving around me. This created a serious risk of a rear-end collision or crash. Additionally, after the dealer visit, the electrical system began failing and the vehicle has been completely dead every morning, leaving me stranded with a child and unable to reliably start the car. The problem has not been reproduced because the check engine code cleared itself after the incident; however, the symptoms absolutely remain. The dealer refused to diagnose the loss-of-power event because the code was cleared, and they returned the vehicle to me with a dead battery. The electrical issue (car dying every morning) has been happening consistently since the dealer visit. The vehicle was taken to a Hyundai dealership immediately after the incident, but they refused to diagnose the loss of power due to the code being cleared. A mobile mechanic scanned the code at my home before the tow, but the code disappeared afterward. The electrical failure began after the dealer visit and has not been properly inspected by Hyundai. Yes. While driving on the highway, the check engine light came on and the car immediately lost power and would not accelerate. After the dealer visit, the car has been completely dead every morning and requires a jump to start. These symptoms began on the same day as the highway incident and continued after Hyundai serviced the vehicle.

Filed Oct 10, 2025 · Engine, Fuel system · FL

The problem with my vehicle is a failure of internal engine components, specifically a known defect in the piston rings of the Hyundai Theta II engine. This failure causes excessive oil consumption, which is burned internally. The internal engine components have failed, leading to a widely documented defect in the Hyundai Theta II engine. The primary symptom, which began to get serious around 80,000 miles, is the constant need to add oil to the engine every two weeks. If I do not do this, the low oil warning light illuminates on the dashboard, serving as a continuous alert of the problem. This failure was officially confirmed by an authorized Hyundai dealership. About two weeks ago, they first documented that there were no external leaks on the vehicle. When I returned because the oil had been consumed again, they performed a new diagnostic, for which I paid over $300, that confirmed the engine is burning oil internally. The dealership, acting as the manufacturer's representative, is the only entity that has formally inspected the vehicle. The situation places my safety and the safety of others at serious risk. First, the oil consumption can lead to a sudden and catastrophic engine failure, resulting in a loss of power and control of the vehicle while in transit. More alarmingly, the guidance I received from Hyundai staff was to simply "wait for the engine to stop working or start making a lot of noise." As someone who depends on the car for a daily commute, following this dangerous recommendation is an unacceptable risk.

Filed Jul 24, 2025 · Engine · MO

While driving on the highway, experienced loss of power and flashing check engine light, subsequently causing engine knock and engine failure. This situation could have caused an accident and put myself and others at risk. It is understood the manufacturer has recalled more than one million vehicles due to engine failure and is working with the federal safety agency to address the issue. In communication with the manufacturer to inspect the damage and resolve the issue.

Filed Jul 22, 2025 · Engine · WA

Rod bearing failed at highway speeds, loss of power and flashing check engine light only after engine failure. This could have caused an accident putting myself and others at risk of bodily damage had I not been able to pull off of the freeway. Engine knock/rattle, eventually leading to catastrophic engine failure. This has been confirmed by a third party trusted and certified technician at an independent shop. Currently in the process of having the damage inspected by the manufacturer.