2018 Hyundai Sonata Powertrain (other) Problems

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.

NHTSA ID

11744559

Incident

Jun 14, 2026

Following completion of Service Campaign 9C2 (ECU software update, TSB 25-01-087H) at a Hyundai dealership, my 2018 Sonata immediately exhibited drivability changes that were not present before the service. Symptoms include altered shift timing, hesitation, and rougher throttle response — particularly noticeable during the first several minutes of driving. These symptoms began on the first drive after the recall update was applied and have been consistent since. The vehicle was returned to the dealership for inspection. No underlying mechanical issue was found, confirming the drivability change is directly attributable to the ECU software update. The vehicle has been maintained strictly per Hyundai's manufacturer-recommended schedule and had no prior drivability issues. I am aware that numerous other owners of Theta II-equipped vehicles (Sonata, Santa Fe, Tucson) have reported identical symptoms following 9C2. At least one dealership has reportedly acknowledged this as a known post-update issue that Hyundai is working to resolve. The altered throttle and shift behavior poses a safety concern, as unexpected hesitation during acceleration affects predictable vehicle control in traffic. The vehicle is available for inspection upon request.

NHTSA ID

11743622

Incident

Mar 14, 2026

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.

NHTSA ID

11740030

Incident

May 14, 2026

Mileage

47,575 mi

Engine blown out malfunction took two dealer Hyundai Folsom Lake stated rings are bad sludge buildup in engine and stayed at Hyundai motor America denied engine replacement due to knowledge under Theta two engine extended warranty settlement of 150,000 MI 15 years I'm still within warranty but are still being denied had numerous of issues with vehicle oil consumption knock knock sensor replace and other maintenance done since purchase vehicle brand new in 2018

NHTSA ID

11737468

Incident

Apr 4, 2026

The vehicle developed a progressive engine failure beginning in early 2024, including loud knocking noises at cold start and visible white/gray/black exhaust smoke. The condition worsened over time. In February 2026, the failure escalated to active oil discharge from the exhaust pipe while the engine was running. Oil exiting through the exhaust indicates internal engine failure (such as piston rings, cylinder walls, or valve seal failure), not an external leak. This creates a safety risk including potential loss of power while driving, risk of engine seizure, and possible fire hazard due to oil in the exhaust system. The condition has been documented on video multiple times and was shown to dealership personnel. The vehicle was taken to a Hyundai dealership for evaluation and remains available for inspection. Despite this, no written diagnostic findings or repair determination have been provided. The issue has been persistent, progressive, and reproducible, and represents a potential defect affecting engine integrity and safe operation of the vehicle.

NHTSA ID

11726107

Incident

Jan 31, 2026

I bought a 2018 Hyundai Sonata a few years back. No warranty. Used. 110,000 miles. A few short months after I purchased it, it stopped working. I took it back to the same dealership where I purchased it and they said they had to replace the coil packs and spark plugs and clean something in the engine out because there's a defect in the engine. I paid $500. Fast forward a few months later. Same thing happens. I take it to an auto repair shop because it's cheaper and the mechanic says he deals with these same issues with other customers who have similar year, make, and models. This pattern continues to this very day. It broke down while I was working my 2nd job. I have a daughter. She plays sports. I have a second job. I need this problem completely alleviated as quickly as possible. Like a lot of the American public, I don't have extra money to keep up with anything beyond the normal maintenance of my vehicle. I keep it up to date with all oil changes. What can you do to get me a vehicle I can trust and it not break down every couple months and cost $300-$600 each time? I don't have good credit (I'm working on that) I have medical issues that I have to visit my doctor for every 3 months. I have the loan through Capital One and they don't offer refinancing. My father who has passed was a car salesman his entire career. I just need reliable transportation and if it's a motor problem like they say then I shouldn't be liable to fix it. The manufacturer should. Please let me know if you need any service records from me. Oh and I also have to put about $20 worth of oil in it every week or so between oil changes. My local oil change guys unfortunately know me very well.

NHTSA ID

11726097

Incident

Mar 21, 2026

The vehicle had safety and mechanical problems shortly after purchase, even with low mileage. The issues included warning lights, abnormal noises, repeated mechanical failures, and poor performance that affected the safe operation of the vehicle. These problems started early and continued over time despite repairs and maintenance. Before the incident, the vehicle showed signs of malfunction, including instability while driving and loss of normal performance. These symptoms created an unsafe driving condition and increased the risk of a crash. I believe the vehicle had defects from the beginning that affected safety. The failure contributed to the accident that occurred while driving on the highway, putting my life and my family at risk.

NHTSA ID

11724392

Incident

Mar 16, 2023

Unknown what system failed. The vehicle is at an impound lot and can be inspected on request. Police and fire department were on the scene. Police did provide a report # , and fire department provided a fire rescue case number. Safety of driver was put at risk due to the fire and potential for burning or even death. Other drivers could have been at risk if traffic had not allowed for quick movement to side of the road. No warning lamps had been on prior to the drive and none prior to fire. First indication was a burning smell while driving. As pulling over, another driver honked to alert to fire he could see from rear of ca,. before I noticed the flames. Upon getting out of car first flames I saw appeared to be coming from under passenger side of car. The fire department arrived about 15 minutes after pulling to side of the road. The car was fully engulfed in flames. They then extinguished the fire. Police saw vehicle and insurance will examine. Apparently this is a known issue in Hyundai of which this vehicle had no open recalls pertaining to such.

NHTSA ID

11714245

Incident

Jan 29, 2026

While driving on the highway, my 2018 Hyundai Sonata experienced sudden loss of engine power and became undrivable. The failure occurred without warning at approximately 86,500 miles. At the time of the incident, there were two children in the vehicle, and the breakdown occurred at night in cold temperatures (approximately 20°F). An authorized Hyundai dealership later diagnosed zero compression in cylinder 3 and confirmed a cracked piston, recommending full engine replacement. The sudden loss of power while driving created a safety risk due to traffic conditions and environmental exposure.

NHTSA ID

11705457

Incident

Nov 27, 2025

During multiple dealership visits in 2025, my 2018 Hyundai Sonata Limited 2.0T was repeatedly returned in unsafe condition. Southern Hyundai installed both front CV axles and torqued them incorrectly. The right axle was later confirmed under-torqued by about 50 ft-lbs, and the left axle was later found over-torqued 40ft-lbs Priority Hyundai later identified and corrected the under-torqued right axle, which briefly improved symptoms but did not resolve the underlying issue. When I returned for a follow-up on October 29, 2025, for a documentation-only appointment due to an active corporate case, the dealer ignored my instructions and altered evidence by loosening and re-torquing the left axle nut without consent. They recorded the torque at 250 ft-lbs in the repair order but failed to capture the required photos or before/after readings and referenced the wrong vehicle’s torque specification (Hyundai Elantra) in the documentation. Since then, the vehicle has continued to show steering pull, vibration, and instability at speed. Several visits showed only 0–3 miles of verification driving after safety-critical repairs involving brakes, suspension, and driveline components. Aftermarket parts were installed when OEM parts were promised, and uneven tire wear developed quickly. Safety risks include wheel-bearing damage, steering loss, and driveline separation due to repeated improper torque and altered evidence. Independent Firestone and Honda technicians have verified these issues. The matter remains under active Hyundai Corporate Case #[XXX]. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11698025

Incident

Oct 29, 2025

Engine failure. Definitely a safety issue, check engine light flashing, limited engine power. Wouldn’t accelerate. Dealer inspected, there is a nationwide recall and class action lawsuits and they won’t replace even though it’s under warranty. False information saying maintenance neglect on my part. That is FALSE. Known failure and oil consumption. Rod bearing failure.

NHTSA ID

11679941

Incident

May 28, 2025

The contact owned a 2018 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, the vehicle sputtered, jerked, and lost motive power. The check engine warning light was illuminated. The vehicle was able to restart but made an abnormal ticking sound. The vehicle was taken to the dealer but was not diagnosed or repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 72,000.

NHTSA ID

11678701

Incident

Aug 6, 2025

Mileage

72,000 mi

The engine shuts off, doesn’t start, check engine light flashing, losses power, jerks while driving it, i will get it up yo speed then will shut off or won’t move.

NHTSA ID

11671246

Incident

Jan 2, 2025

The car in recent months has twice lost power and been rendered in operable on the side of the road until it could be limped home. I had the car serviced last year for a recall of a fuel filter gasket and at that time I was informed that I also had an update done for a (k knock?) sensor prior done on the car before purchase. I inquired about what that was, and they told me at the time it was for an engine recall because that particular engine I have is known to have rod bearing failure and consume oil without any trace of where it goes and piston rattle. I told the gentleman after my fuel gasket was taken care of that I would like to look into that because I have the symptoms and would like to know. At that point in time, I was told that I may have to do an oil test to see if the car loses oil. I said well can we do that and he told me it's $300 out of pocket. I asked on average before anything ever done by Hyundai, how many times do people have to do this? He said 4 to 6 in his experience. I told him I did not have the money, but I will keep an eye on the car. Everything's been fine for six months a few months ago Randomly driving to work the car shut down on me. We got the car home and my fiancé did an oil change and new spark plugs and the car worked fine. June 9th 2025 on my way to work the issue happened again in the middle of traffic. I called my fiancé and we got the car home. He performed another oil change and spark plug replacement and took pictures this time because the spark plugs are gunked up. The car now runs again. He called Hyundai of America on my behalf to just ask them if they could set up the test to see if the car was failing and they told him that they were all independent Hyundai and he would have to pay the test fees. He told them in a formal email that he doesn't believe under the federal recall He is responsible for that and they answered back that he may be reimbursed. We are contacting you because we were advised to on the issue

NHTSA ID

11666433

Incident

Jun 9, 2025

The car went into limp mode they have problems with the knock sensor and that is what it threw to the computer and I changed the sensor and went away and now limp mode again and computer says basically the same thing there is a software update and the engines are failing

NHTSA ID

11656177

Incident

Apr 11, 2025

The engine stalls when driving, loses power, hard time to start. It uses an extensive amount of oil. Losing power/stalling can result in accident or fire in my engine. Yes check engine light came on said it was coils/plugs changed them 2xs already. Took it to a mechanic was told there’s a recall on engine it’s a valve that is not getting air through that can potentially case a Fire in my engine.

NHTSA ID

11656049

Incident

Jan 5, 2025

My 2018 Hyundai Sonata (approx. 60,000 miles) began consuming excessive oil, and the engine started smoking while driving. My wife barely made it to the dealership — the car was unsafe, struggled to stay running, and visibly smoked from under the hood. Hyundai acknowledged the oil issue but refused to cover engine replacement. Instead, they approved a one-time combustion chamber cleaning and requested we drive the car 1,000 miles to "see if it gets better." This is a major safety concern. The vehicle is part of a group of Hyundai models known to have defective Theta II engines that have led to engine failure, fire risk, and recalls. This issue is widespread, and Hyundai is not taking proper responsibility for defective engines in cars like mine.

NHTSA ID

11651132

Incident

Mar 20, 2025

I was going 80 mph on the interstate and suddenly my car went into limp mode and shooked really hard and dropped to 60 mph. I had to swerve to go onto the side of the road. The car behind me almost rammed into me. I contacted hampton hyundai for days to schedule an appt. I finally was able to drop off my vehicle to them but now they are telling me they have to do an oil consumption test but my car is in limp mode and it shakes when I drive it. The car is dangerous and they are trying to charge me $500 for a fuel pump replacement ( which I have a warranty of but they notified me that does not count but it matches exactly the possible reason). As you can see in the documents, they did not note that my fuel pump was broken. They just asked if I wanted to pay it so they can get started. I get normal oil changes done. They haven't even done a rod bearing test but just looked at the knock sensor and was telling me that they wanted to charge me to get that changed.

NHTSA ID

11648883

Incident

Mar 10, 2025

When my car suddenly stopped on the highway, I encountered an issue with the “body control module.” The car wouldn’t start, and the key fob was ineffective. Additionally, the airbags stopped working. I don’t recall all the details, but I was unsure of where to report the dangerous vehicle. I’ve noticed several other Hyundai owners complaining about this issue, where their cars suddenly stop in the middle of nowhere.

NHTSA ID

11632977

Incident

Jul 22, 2023

My car is part of a campaign due to rod-bearing failure where the engine experiences problems such as complete failure, vibrating, hesitating, engine light on, and oil light on. I've been communicating with Hyundai who is not helping me with this issue. I was advised by them to continue driving the car "until the engine seizes", or I hear "a loud knocking noise". Upon inspection, three local Hyundai employees "agreed 100%" I need a new engine. However, per these employees Hyundai Corporate will not approve the replacement even though the vehicle is constantly experiencing the above symptoms above, simply because there is not a "loud knocking noise" coming from the engine. Even though ALL the other issues are present. This is very unsafe. I have a minor child I take to school daily, for an advisor to advise to drive the vehicle until "the engine seizes" is extremely dangerous, especially when they are aware my VIN is associated with engine replacement. My car exhibits symptoms of a rod-bearing failure and this multi-billion dollar company is taking advantage of hard-working urban mothers, by turning a blind eye and trying to require me to pay thousands of dollars up front for a problem THEY created by selling a vehicle with faulty engine. Again, the technicians indicated i in fact do need the engine replaced, but that Hyundai Corporate will require me to pay for a diagnostic test, rod-bearing test, and engine compression test because Corporate does not take their word for it. The fact a auto manufacturer is advising people to drive in such an unsafe manner is disheartening. If my child and I get injured in an accident by following their advice, our blood will be on their hands!

NHTSA ID

11622145

Incident

Jun 1, 2024

Severe oil leak into the oil pan has required frequent maintenance to keep oil in the car.

NHTSA ID

11578109

Incident

Jan 15, 2023

On [XXX] I was driving on [XXX] [XXX] from Rockville, Maryland when my vehicle (2018 Hyundai Sonata Limited) started to lose power and control and all dash lights started to show. I was able to move the vehicle to the highway shoulder before all power and control failed. Had I been moving at a higher speed or in heavier traffic, or been slower to react this could have led to a catastrophic incident. When the roadside assistance showed up they found that my alternator had completely detached from my vehicle. The vehicle was towed to the Sheehy Hyundai dealership in Waldorf, MD and examined on [XXX]. The maintenance staff informed me that there were 3 other similar cases they're working on, and that there is a flaw in the design of the alternator bracket using aluminum materials that failed, and that they've reported this systemic issue to the manufacturer but have yet to receive any indications that this would be considered for a recall despite the catastrophic impact this could have. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11576236

Incident

Mar 6, 2024

Starter replaced at less than 50,000 miles. Normally a starter will last 150,000 miles or more. I was past the warranty by 9 months but was under the mileage. Warranty was 5 years or 50,000 miles. Hyundai parts are cheap and do not last long compared to other companies.

NHTSA ID

11567695

Incident

Aug 4, 2023

I have had a new engine put in my Sonata back at the beginning of 2023. For the past two days my car will jerk really hard, and then loose power not accelerating over 25 rpms and my check engine lights comes on when it jerks really hard.

NHTSA ID

11566992

Incident

Jan 21, 2024

The contact owns a 2018 Hyundai Sonata. The contact stated while driving 70 MPH, the vehicle went into LIMP Mode and lost motive power. The contact was able to pull to the side of the roadway, where the vehicle failed to restart. The check engine warning light was illuminated. The vehicle was towed to an independent mechanic, who determined that cylinder #1 was misfiring on every cycle due to damage to the piston. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was 107,000.

NHTSA ID

11559172

Incident

Nov 29, 2023

Mileage

107,000 mi