Engine And Engine Cooling Problems of Hyundai Sonata - part 1

I was driving my 2014 Hyundai Sonata that I only had for 3 months when it just quit on me. I pulled over and seen when white smoke was coming from the wires.

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Updated NHTSA complaint draftvehicle information: 2014 Hyundai Sonatavin: [xxx] incident date: xxx description of safety defect:while driving on xxx, the vehicle's engine experienced a catastrophic mechanical failure and completely shut off without warning, causing an immediate loss of motive power. This sudden engine stall created an extreme, hazardous traffic safety risk. A subsequent professional inspection revealed that the vehicle's odometer had been illegally rolled back and tampered with by the selling dealership (johny's auto center in 120 bleu hill Ave roxbury, MA) 02119 prior to purchase. The true, undocumented mileage of the engine is significantly higher than indicated, directly causing this sudden component failure. I am reporting this incident both as a critical vehicle safety defect and as a case of illegal odometer fraud. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

At approximately 130,000 miles, vehicle developed and internal coolant leak caused by a failed exhaust heat recovery system (ehrs) in the center muffler assembly, matching TSB 23-em-009h - a known manufacturing defect documented by Hyundai. Coolant has been slowly leaking internally into the exhaust system. The authorized Hyundai dealership initially failed to diagnose the internal leak and told me there was no leak and wanted to send me home. After pushing back, the internal leak was confirmed. If not caught, this defect could result in engine overheating or complete engine failure without warning. Hyundai motor America has denied goodwill coverage despite this being a documented manufacturing defect.

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I am writing about my 2013 Hyundai Sonata VIN: [xxx]. On [xxx] my vehicle experienced a knocking noise from the engine and the illumination of the check engine light. The car lost power and I was unable to drive it home. I had to call a tow service to have the car towed to alan turner Hyundai, 6501 pensacola blvd, pensacola, FL 32505. I spoke to a service writer at alan turner Hyundai. He told us that they could not help us and to contact Hyundai corporate office for help. We purchased this car brand new from alan turner Hyundai. We visited your web site and put in our VIN and the system stated that our vehicle was affected by the Sonata and santa fe sport engine recall campaign. We are an [xxx] with one car, and that car has stopped working. We need help in getting this car repaired under warranty via the Sonata and santa fe sport engine recall campaign. Thank you. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

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Check engine light solid/engine failure while driving. 2018 Sonata se purchased new in fall 2018. Around 50,000 miles started noticing oil level drop and had to add more before next scheduled change. Dealership service center said I just had to shorten the mileage between changes which didn't seem appropriate for a vehicle with 50,000 miles but I did. Continued to have oil consumption problem with no signs of leak, no burning oil smell or exhaust issues. Dashboard display would go off and when I immediately checked dipstick there was barely any oil so I'd add more then go in for full change. At 67,000 or so miles in June 2026, without oil display going off the engine light was now solid. Got to reputable service center near my home and oil was under a quart left yet the warning lamp hadn't gone off. They ran the engine error code p0304 and was misfire #4 cylinder and after compression test, #3 was very low and #4 very high. Not drivable at that point then towed to dealership so yes, available for inspection by NHTSA at the dealership. For now they claim a 'tune up' is needed for spark plug replacement, valve cover gasket replace and fuel induction service that's my cost to incur which seems to just be fixing the damage of an engine oil consumption problem not fixing the issue that caused the damage. The engine seized/stalled without warning while I was driving the vehicle (granted at low speed in my neighborhood when the engine light turned on). I would not say the engine warning lamp occurred prior to the engine fail, it happed at the same time. This should not happen for a vehicle with my mileage and regular maintenance. I looked up NHTSA for potential recall or other helpful information and started to see extremely similar scenarios to mine and wanted to add complaint as well. This is getting very expensive outside of whatever cost the dealer wants as a fix with rental car needed and tow services. Thank you for your consideration of this engine safety issue.

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The contact owns a 2015 Hyundai Sonata. The contact stated that while idling at a stop light the vehicle suddenly stalled. The engine did not restart and the vehicle was pushed to a nearby parking space. During the failure no warning lights or messages had displayed. The cause of the failure was not yet determined. The manufacturer and local dealer were not yet contacted regarding the failure. The failure mileage was 123,000.

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After the emissions 9c2 recall car hesitant when changing an Hyundai has knowledgement of the problem but don’t have a fix.

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For my vehicle the check engine light has been on continuously throughout the last 6 months and mechanics are going to have to replace the thermostat. Multiple auto mechanics have indicated online that this is a very common problem with many Hyundai vehicles from 2020-2023 and can be a danger due to temperature control not being accurate for vehicles (code p2181). Many owners of these Hyundai vehicles have experienced this issue leading online and this issue should be made aware to Hyundai and the general public to see if this is something that needs to be made aware for the safety of drivers to determine if their vehicle is at an accurate temperature.

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The vehicle is stalling in the acceleration process. I can feel and hear the stall by the air conditioner going out or fading out when it happens while driving. Pressing the gas and it barely moves at times. Makes a noise now while running. Unknown to whether it's electrical or engine or transmission. Pull out in the traffic accelerating but the car wasn't moving at the pace it should have. Could have cause an accident when trying to cross on going traffic. Just got the vehicle 2 weeks ago. No one has inspected the vehicle yet. Going to have it looked at for recalls. No warning lights appeared to reflect an issue, but there clearly is.

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[xxx] [xxx] [xxx]; [xxx] [xxx] [xxx] date: xxx 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).

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Was driving the vehicle up berthoud pass on [xxx] . Was a few miles past berthoud falls and realized that the vehicle power diminished, noticed smoke coming from the engine. Pulled over and noticed leaking underneath the engine. It appears that a bolt came loose and punctured the engine block. After further research, it appears that this engine recall should have applied to my vehicle, but did not: [xxx] information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

I am submitting this complaint regarding a serious safety issue involving my Hyundai Sonata. While driving under normal conditions, my vehicle suddenly entered a low-power ("limp") mode without warning. The vehicle would not accelerate beyond approximately 30–35 mph, creating a potentially hazardous situation in traffic. At the same time, the check engine light began blinking. The sudden loss of power significantly reduced my ability to maintain traffic speed and safely maneuver the vehicle. This condition could have increased the risk of a rear-end collision or other accident. I brought the vehicle to an authorized Hyundai dealership (fred beans Honda of abington ph# 215-392-9020) for diagnosis. The dealership confirmed that the vehicle stored diagnostic trouble code (dtc) p1326, related to the knock sensor detection system (ksds). According to the dealership, the vehicle entered limp mode as a result of this fault. The abrupt reduction in vehicle power and speed occurred without sufficient warning and created a safety concern. I am reporting this incident so that NHTSA can investigate whether this condition represents a broader safety defect affecting Hyundai Sonata vehicles equipped with the ksds system. Vehicle information: make: Hyundai model: Sonata model year: 2014 I request that NHTSA review this issue and evaluate whether additional action is warranted regarding vehicles experiencing dtc p1326 and associated limp-mode operation.

Knock sensor needs to be replaced upon evaluation of an inspection on March 27, 2026. It failed a mission codes and upon my understanding the knock sensor one circuit range performance pink wonder single sensor is an engine failure as well as I did an odb test myself on may 19 of 2026 for the knox sensor as well and the check engine dominator reading at 2111 the the code indicated that bank one knox and electrical circuit was out of it upper range or had it perform problem for a predetermined period of time and the code is p0326 and the secondary dtc is a combustion vibration sensor a circuit range performance which affects the powertrain. Also, I have switches with the electrical features in the vehicle as far as the abs and the steering wheel controls and glitching for the cigarette adapter and plug-in area as well on top of the rear passenger side window, having issues with going up and down.

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The contact owns a 2021 Hyundai Sonata. The contact stated while driving at an undisclosed speed, the engine shuddered and the engine stalled. In addition, the engine seized. No warning lights were illuminated. The contact stated that the vehicle was seized in the middle of the road. The contact stated that while attempting to start the vehicle, the vehicle started. The failure reoccurred. The vehicle was towed to the residence. The vehicle was not diagnosed or repaired by an independent mechanic or dealer. The manufacturer was made aware of the failure. The failure mileage was approximately 140,000.

My 2020 Hyundai Sonata 2. 5l is experiencing excessive engine oil consumption. At approximately 88,063 miles, great lakes Hyundai documented that the engine oil level was 1. 30 quarts below full after an oil-consumption check. The dealer topped off the oil, submitted photos and a prior-authorization/goodwill request to Hyundai, and Hyundai declined assistance. The dealer recommended combustion chamber cleaning with an estimate of $979. 76. I am concerned that this excessive oil consumption could lead to sudden engine damage, loss of power, stalling, or engine failure if the oil level drops between checks. The vehicle is only a 2020 model year, and this level of oil consumption appears abnormal. I am also concerned about possible emissions/catalytic converter damage from oil burning.

Went from 65 and dropped down to 40 going up grades on the freeway. Started shaking, check engine light went on and electric battery disappeared from dash. Got to top of grade, went back to normal. Problem repeated on next grades. Car had just left dealership lot an hour prior where it was safety inspected and they said all was fine. Took back to dealership for inspection and they said that there were no codes showing for what happened and all was well with the vehicle, when obviously it was not.

The contact owns a 2016 Hyundai Sonata. The contact stated that while driving approximately 60 mph, the vehicle suddenly shut off with the message "hev system failure" displayed. The driver safely pulled over to the side of the road and restarted the vehicle. A towing truck arrived on the scene and reset the diagnostic codes before towing the vehicle. The vehicle was towed to the local dealer. The dealer retrieved several diagnostic trouble codes; however, the dealer was unable to determine the cause of the failure. The vehicle was test-driven but the failure was not duplicated. The vehicle was not diagnosed or repaired. The manufacturer was notified of the failure. The failure mileage was approximately 149,000.

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 contact the contact stated that when taken the vehicle for a service campaign repair and shortly after went for recall r the vehicle does not run properly on cold starts, the rpms increase rapidly and slow down, vehicle jerks forward once beginning to drive. . The vehicle does not have this issue once the vehicle is warm. The manufacturer was not notified of the issue. The approximate. Failure mileage was 47,575.

After completion of Hyundai service campaign 9c2, my 2016 Hyundai Sonata se is very difficult to drive at low rpms. Cold start its sluggish and jerks and driving uphill feels like transmission slipping but is not. An additional update to the ecm needs to be conducted ASAP.

The contact owns a 2015 Hyundai Sonata. The contact stated while driving at various speeds, the vehicle skipped and failed to exceed 35 mph. The contact received notification of Hyundai service campaign number: 9c2 (ecu software update for theta ii emissions improvement), and the vehicle was towed to the dealer, where it was diagnosed and determined that the catalytic converter was clogged and needed to be replaced at the owner's expense. The vehicle was not yet repaired. The contact's son, who was an independent mechanic, determined that the ecu might have sent erroneous signals to the O2 sensors, who then sent excessive fuel into the catalytic converter, causing a catalytic converter clog. The manufacturer was notified of the failure and was informed of the service campaign notification, but the manufacturer denied assistance due to the mileage and lack of warranty coverage. The failure mileage was approximately 140,000.

I went shopping notice needed gasoline filled the tank 3/4 the next day I smell gasoline on my2013 Sonata hybrid VIN [xxx] inside the car and I did not notice any light alerts etc. , just the smell of gasoline inside the car. I ask for a ride I was scare to drive to the dealer on Monday 5/6/26 around 12:30 pm I called the dealer I was gonna dropped the car they told me diagnostic would take 3 days , I was afraid to cut on fire since my gas left a big stain and was wet gasoline in the parking lot at work. , I called Hyundai USA mentioned the problem I notice there is a recall for gas pump leaking and causes gas tank to crack recall for 17v-226 for fuel pump leaking 0n Hyundai Sonatas hybrid 2011-2016 my car is in the Hyundai dealership [xxx] [xxx] they called me telling me my gas tank is cracked cost of repair labor 2800. 00 and 280. 00 diagnostic charge and is ready for pick in 30 min no recalls I must pay for this service information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

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.

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.

The contact's son owns a 2015 Hyundai Sonata. The contact stated that while the vehicle was being driven at 40-50 mph, the vehicle began to jerk. The check engine light was illuminated. The vehicle was taken to an independent mechanic who determined the failure was related to the engine. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 102,198.

Consistent burning of oil.

P1326, rod bearing failure and seizure of motor without warning.

Unknown.

2015 Hyundai Sonata 2. 4l theta ii gdi engine experienced complete failure due to connecting rod bearing defect. Vehicle was taken to a Hyundai dealership prior to failure to report engine knock symptoms. Dealer confirmed ksds (service campaign 953) was installed but performed no inspection and provided no repair order. Engine subsequently failed with no warning light activation despite ksds being installed. This is a known defect covered under the theta ii class action settlement lifetime warranty. Warranty repair has not been provided and no loner car has been provided.

My 2016 Hyundai Sonata is experiencing severe oil consumption due to a known Hyundai engine defect. The engine burns oil rapidly and loses more than a quart between oil changes. This creates a safety hazard because the engine can stall, seize, or fail while driving. The Hyundai dealership did not perform the official Hyundai oil-consumption test. They only checked the dipstick, noted the oil was low, and submitted a request for a paid combustion cleaning. Hyundai declined to pay for the cleaning, and the dealership is refusing to perform the required oil-consumption test unless I pay $750. 00. Hyundai corporate also refused to authorize the test, stating the vehicle is out of warranty, even though this is a known engine defect affecting many Hyundai vehicles. Without the official test, Hyundai will not review the engine defect or consider a goodwill engine replacement. This is a safety issue because the engine can fail without warning. The dealership and Hyundai are refusing to perform the required diagnostic test unless I pay $750, and refusing to review the defect without that test.

Ecm, p0303, yes, not yet, no, cel light before the car was brought to the dealership, 2019 Hyundai Sonata se, 2. 4l theta ii gdi. Perryville Hyundai IL refused applicable TSB in writing 5/4/26 despite active p0303 misfire, fuel-in-oil smell, crankcase pressure. I have photos prove falsified multi-point inspection: 1. 0 inch (. 0833') wheel well discrepancy, same mileage in/out. Vehicle has stall risk. Case manager [xxx] non-responsive 2hr 45min after requesting written tow instructions on safety matter. Rspm escalated 1:00 pm cdt 5/5/26 with 3:00 pm deadline. No contact received as of 3:03 pm. Vehicle unsafe to drive. Theta ii lifetime warranty settlement violation. Case #xxx. Requesting federal investigation. Photo upload is not working, I'll need a email to send them in apparently information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

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On 5/27/2026 I was driving home from work. Had just gotten off the frwy , was driving around 35-40mph, all of a sudden , engine turned off, after coming to a stop, holding up traffic, I put in park, and nothing, not crancking, a new battery was imstalled, 3 weeks prior, have recoreds of all maintenance! checked oil level was good, radiator, had fluid, and fas tank was 1/2 full! pushed to a side street ,uberd, back home, later that evening , had car towed approx 5 miles to my house. Checked all fuses, ignition, and starter! spoke with local hundai dealership, scheduled a maintenance diagnostic to be performed! could have been an accident, first time, ever experienced, such an issue!.

The contact owns a 2011 Hyundai Sonata. The contact stated that while driving at 60 mph, the vehicle lost automotive power. There was no warning light illuminated. The vehicle failed to restart and had to be towed. The vehicle was towed to the dealer, but was not diagnosed or repaired. The manufacturer was made aware of the failure. The failure mileage was approximately 190,000.

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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.

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.