2018 Hyundai Sonata problems

POWER TRAIN

I recently had the 9C2 Emissions recall update performed on my car, and since the update my car drives like total garbage after a cold start. It hesitates to accelerate, it bucks when trying to accelerate, and it’s to the point the engine is about to stall. I took it back to the Hyundai dealership and they said they are aware of the issue, but there is no fix from Hyundai at this time. This is a major safety concern, as the car barely wants to accelerate after a cold start. Please have Hyundai fix this safety issue.

NHTSA complaint #11757253 — an unverified report by a vehicle owner.

STRUCTURE:BODY

The paint on all parts of the car is completely coming off down to bare metal. It’s as if the car wasn’t prepped to receive paint. Every Hyundai I pass that’s white the paint is coming off. There is also an internal engine oil leak where I’m losing 4qts of oil a week.

NHTSA complaint #11757263 — an unverified report by a vehicle owner.

ENGINE

I recently had the 9C2 Emissions recall update performed on my car, and since the update my car drives like total garbage after a cold start. It hesitates to accelerate, it bucks when trying to accelerate, and it’s to the point the engine is about to stall. I took it back to the Hyundai dealership and they said they are aware of the issue, but there is no fix from Hyundai at this time. This is a major safety concern, as the car barely wants to accelerate after a cold start. Please have Hyundai fix this safety issue.

NHTSA complaint #11757253 — an unverified report by a vehicle owner.

ENGINE

The paint on all parts of the car is completely coming off down to bare metal. It’s as if the car wasn’t prepped to receive paint. Every Hyundai I pass that’s white the paint is coming off. There is also an internal engine oil leak where I’m losing 4qts of oil a week.

NHTSA complaint #11757263 — an unverified report by a vehicle owner.

FUEL SYSTEM, GASOLINE

The contact owns a 2018 Hyundai Sonata. The contact stated that while operating the vehicle, there was an abnormal fuel odor inside the vehicle. The vehicle was taken to the local dealer and was diagnosed with an inoperable low-pressure fuel pump. The contact was informed that the low-pressure fuel pump needed to be replaced. The vehicle was not yet repaired. The manufacturer was notified of the failure. The contact stated that the manufacturer had issued an extended warranty coverage for the failure. The failure mileage was 92,000.

NHTSA complaint #11752670 — an unverified report by a vehicle owner.

ENGINE

The lower aluminum engine oil pan developed a structural hairline fracture ("micro-crack") directly along the factory casting ridge adjacent to the drain plug. The component failed without any external impact, road hazard, scraping, or underbody damage. The failure was officially confirmed and documented by Eckert Hyundai during a service visit on July 13, 2026 (Case #42971835). Following the dealer oil service, the fracture degraded into an active, worsening oil drip that requires a catch tray under the vehicle to capture leaking fluid. The vehicle is currently available for inspection. Safety Risk: An active engine oil leak poses a significant safety hazard. Rapid or continuous loss of engine oil can cause sudden oil starvation, severe engine seizure, or total power loss without warning while driving at highway speeds, increasing the risk of a crash. Furthermore, dripping oil contacting hot exhaust or engine components presents a potential fire hazard. Prior Symptoms / History: This vehicle has a well-documented history of severe internal engine issues and thermal stress, including excessive oil consumption (running 1.2 quarts low in 1,127 miles), valve cover gasket failure, and severe drivetrain vibrations from failing front axles. The excessive internal crankcase pressure and thermal stress from these underlying defects contributed directly to the material fatigue and structural failure of this aluminum oil pan.

NHTSA complaint #11751641 — an unverified report by a vehicle owner.

FUEL/PROPULSION SYSTEM

Fuel line leak, car is parked, fire hazard, a mechanic has been there to inspect

NHTSA complaint #11749020 — an unverified report by a vehicle owner.

ENGINE

I purchased my vehical at Car Culture in Warren, Oh. The dealer said to only take it there for maintenance, so I did as required. Whenever the check engine light came on I would bring it there and they would say it was a sensor and they fixed it. And one day it started miss firing and the light came on again. When I took it to the dealership, they said it needed oil to bring it in every 2 weeks to top the oil off. And so I did that and finally the car was getting worse at 122,000 miles. When I took it there they said it needed a new motor!!!. They NEVER told me of a recall or a sensor replacement needing done by hyundai. Iam now stuck with a $13,000 loan on a car worth nothing without paying $5,000 on a "possible" fix for their negligence. I have a [XXX] old son, fiancee, morgage and a job im struggling to get to, because I was never notified of a possible recall on my year, make and model of car. Please help me. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11748511 — an unverified report by a vehicle owner.

POWER TRAIN

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 complaint #11744559 — an unverified report by a vehicle owner.

ENGINE

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 complaint #11744559 — an unverified report by a vehicle owner.

UNKNOWN OR OTHER

I was only in the car for about 4 minutes then came to a stop light. Once the light had turned green I pressured down on the gas, my car rolled for a second then died on me, causing it to go into accessory mode. Instantly three lights came on: the check engine light, battery light, and low oil light. The car would take at least 5 seconds to turn back on then would fall back into accessory mode randomly. Tried to jump the car 4 times, issue still remains. What sucks about this is that the mechanic shop can’t even figure out what’s wrong. They thought it was the high pressure fuel pump..turns out it’s not.

NHTSA complaint #11743841 — an unverified report by a vehicle owner.

POWER TRAIN

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 complaint #11743622 — an unverified report by a vehicle owner.

ENGINE

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 complaint #11743622 — an unverified report by a vehicle owner.

POWER TRAIN

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 complaint #11740030 — an unverified report by a vehicle owner.

ENGINE

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 complaint #11740030 — an unverified report by a vehicle owner.

POWER TRAIN

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 complaint #11737468 — an unverified report by a vehicle owner.

ENGINE

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 complaint #11737468 — an unverified report by a vehicle owner.

FUEL/PROPULSION SYSTEM

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 complaint #11737468 — an unverified report by a vehicle owner.

ENGINE

I am submitting this complaint to report a serious and ongoing safety defect involving the engine of my 2018 Hyundai Sonata Sport equipped with the 2.4L Theta II engine. The vehicle has been officially tested and documented by Hyundai as consuming more than two (2) quarts of engine oil per 1,000 miles, which Hyundai has acknowledged following completion of its oil consumption test procedure. Despite this confirmation, Hyundai has declined to fully correct the defect. As the condition has progressed, the engine now fouls spark plugs every 350–500 miles, resulting in: •Engine misfires •Loss of power during operation •Rough running and hesitation •Risk of sudden engine stalls while driving This condition occurs without warning and requires repeated roadside or emergency repairs simply to keep the vehicle operable. The condition has deteriorated further, requiring replacement of fouled spark plugs every 350-500 miles. Loss of power and engine shaking can occur at any time, presenting a safety hazard for me and other drivers.

NHTSA complaint #11736185 — an unverified report by a vehicle owner.

FUEL/PROPULSION SYSTEM

I am submitting this complaint to report a serious and ongoing safety defect involving the engine of my 2018 Hyundai Sonata Sport equipped with the 2.4L Theta II engine. The vehicle has been officially tested and documented by Hyundai as consuming more than two (2) quarts of engine oil per 1,000 miles, which Hyundai has acknowledged following completion of its oil consumption test procedure. Despite this confirmation, Hyundai has declined to fully correct the defect. As the condition has progressed, the engine now fouls spark plugs every 350–500 miles, resulting in: •Engine misfires •Loss of power during operation •Rough running and hesitation •Risk of sudden engine stalls while driving This condition occurs without warning and requires repeated roadside or emergency repairs simply to keep the vehicle operable. The condition has deteriorated further, requiring replacement of fouled spark plugs every 350-500 miles. Loss of power and engine shaking can occur at any time, presenting a safety hazard for me and other drivers.

NHTSA complaint #11736185 — an unverified report by a vehicle owner.

ENGINE

Despite proper maintenance, the vehicle is burning oil at an excessive rate. I have already replaced the oil pan, but the issue persists. I now have to add oil frequently between oil changes. This creates a serious safety concern, as low oil levels can cause engine failure while driving, leading to sudden loss of power or stalling in traffic. This puts me, my passengers, and other drivers at risk. There are no visible leaks, which suggests the oil is being burned internally. This appears to be a potential defect rather than normal wear and tear. I am requesting that this issue be investigated as it may affect other vehicles of the same make and model. This is becoming very expensive having to refill oil as the dipstick shows nothing. This has been confirmed by technicians that there has been no oil in my car despite coming in on time or before the recommended miles. The oil light will come on a few weeks after having the oil changed. It seems this is an issue with this engine type.

NHTSA complaint #11735867 — an unverified report by a vehicle owner.

STRUCTURE:BODY

The trunk latch on the Hyundai Sonata malfunctioned, and our safety was put at risk when the trunk malfunctioned while driving on the freeway, obstructing the back view. After several attempts to try to close the trunk and after doing some research, I learned it had a vehicle recall, 21V619000. An appointment was made at Ontario Hyundai for the latch to be repaired due to the recall. After taking the vehicle in, the dealer stated that an attempt to repair the latch had been attempted and refused to do the repair and provided an invoice of $616.00 for repair. Since the latch malfunctioned, no attempt to repair the latch was ever attempted, nor was it taken anywhere else for repair. The vehicle is available for inspection upon request. The trunk latch is still inoperable, and recall status is incomplete.

NHTSA complaint #11734172 — an unverified report by a vehicle owner.

FUEL/PROPULSION SYSTEM

Throttle response intermittent problem no acceleration since new. No codes available. When entering traffic engine stall factor flat spot. Been to dealer many times (Bud Clary) and just recently (04/26) confirmed the fuel pump is the problem. Unable to confirm because of no "codes". Will not replace or register for recall without proper codes. No check engine lamp. No inspection by police or insurance only the dealership service department is aware of the problem.

NHTSA complaint #11732817 — an unverified report by a vehicle owner.

UNKNOWN OR OTHER

We think there’s an issue with the abs module and wheel speed sensor because we started having a problem where the brakes wouldn’t work or would stutter. The car would shake real bad it would make an awful grinding sound but normally only when trying to stop at higher speeds or long braking. The only thing that made it stop was to unplug the abs but then other parts of the car stopped working like the speedometer and the sensors around the car. So we got the abs replaced but the new one started doing the same thing. We did some research and it sounds like the same issue Hyundai is having with the palisade. The incident that made us get it replaced to begin with was were driving down the road and we got to a traffic light but when we tried to brake they just didn’t work so we drove through the red light luckily the one person who was supposed to be going saw us and didn’t pull out in front of us so we didn’t get hit. We haven’t taken it to the dealership yet but my sister who teaches automotive repair at the community college is the one who diagnosed it so she said we should report it here so maybe it won’t happen to anyone else. Before we had the brake issue we were having problems with basically everything on the dash not working randomly. We’d be driving down the road and the speedometer and the outside sensors and the gas gauge and the traction control all would go out at the same time it’s the same stuff that went out when we had the abs unplugged so it seems that might be related.

NHTSA complaint #11732415 — an unverified report by a vehicle owner.