general problems of the 2015 Hyundai Sonata - part 1

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).

Engine locked up, crank bearing failure, found out there is known failures with this problem and Hyundai had a class action suit against them in the past and issued lifetime warranty for this engine due to this problem. Took car to local dealer, clay cooley in sherman TX, they have been great but Hyundai corporate has denied the claim stating lack of maintenance records. Car has 175,000 miles on it, I have only owned it for about 5-6,000 miles. I have changed the oil in it twice myself I was able to prove one of those with a receipt but I don't have the other receipt and have been unable to get it. The dealer has records of oil changes up to 150k miles then I was able to find additional proof of other oil changes through car fax at smaller lube shops. The previous owner before me changed their own oil also and did not keep receipts I reached out to them with no luck. Ultimately there is only about a 10k mile gap of unprovable maintenance, this engine model has a known issue, it did not make it to 175k miles without proper maintenance, I can't control what previous owners did with their receipts but lifetime warranty should be lifetime not only if you can prove every detail from people you can't control.

I bought this car new in 2015, when I was at 97000 miles they had to replace the motor and turbo, I am now at 155844 and they are telling me that basically all 4 cylinders have low compression, cylinder 3 is the worst. They are telling me that this car has to have a new motor. I have not done anything to this vehicle to cause no compression. They want me to pay around 8800. 00 to get this fixed.

Driving vehicle at slow speed crossing an intersection and engine completely shut down. The engine has completely seized and needs replaced due to a known recall. I have only owned the vehicle for 7 months. Hyundai is refusing to pay for engine replacement claiming a previous recall prior to me owning the vehicle should have been completed. I only drove the vehicle 1,000 miles in that time at nothing over 50 mph. There was no notification to me about this recall.

Engine misfiring and low compression.

Engine / short block assembly / connecting rod bearing seizure. The engine suffered a sudden, catastrophic seizure while I was actively driving on a steep incline mountain road with a cliff on one side and forest on other. The vehicle experienced an immediate, total loss of motive power, forcing an emergency maneuver onto the shoulder in 5 seconds with no power steering or power brakes, creating an extreme collision hazard on a high-speed incline. The rod bearing melted due to a manufacture defect and could have also possible caught fire in heavy fire country. The fuel pump was also leaking recently and just replaced. They are nearly $1800 for a new pump because of price gauging because they are in "high demand". The check engine light was solid (not flashing) for a thermostat code (p0128) due to extreme internal friction/heat from the failing bearings. There were no flashing ksds warnings or physical signs of engine overheating. My car was denied a new engine under a federally mandated warranty explicitly stating the exact symptoms of internal engine defect that happened in my car under "owner neglect" even though I have changed my oil regularly and even before the manufacture recommended time frames to do so. I've changed the valve covers, 02 sensors, thermostats, and plenty more on this car than any other car I have ever owned proving I'm actually an exceptional owner. I remained nice to all corporate staff during this process while they denied my car proper care under a federal mandate. I bought this car to believe that Hyundai was a superior company in regards to warranties, price, and function as opposed to the more expensive counterparts of the same class. Which in the end has cost me way more, and almost my life. This car is dangerous and the company has done everything in their power to try to cover it up while placing blame on the very consumers that are believing in them to do better.

The contact owns a 2015 Hyundai Sonata. The contact stated that the vehicle was taken to a local dealer who performed an emission software upgrade. Later, while driving, the air conditioner blew hot air, the thermostat increased to high, and an engine overheating warning message was displayed on the instrument panel. The vehicle was taken back to the dealer, who diagnosed that the thermostat had failed and needed to be replaced. The thermostat was replaced, and the failure was remedied. The manufacturer was notified of the failure. The failure mileage was 74,000.

I had the service campaign 9c2 and TSB 25-01-087h recall emissions update performed. I immediately noticed degraded performance with my vehicle. It's very jumpy/stuttery after I first start driving and feels less responsive. Even after driving for a bit, it feels like it drives and shifts oddly. It is not as smooth as it used to be. My car drove fine prior to the update and immediately felt different after the update. It's now been over a week and it's still like this, so it's not the engine computer adapting or something like that.

Since the 9c2 update on June 24, 2026, my vehicle has not driven the same. I'm experiencing clunky or harsh gear changes at low speeds, especially during stop-and-go driving. When I slow down and then accelerate again, the vehicle sputters or hesitates before responding. While driving at lower speeds, I also feel intermittent skips or small surges, almost like bubbles or brief misfires. These symptoms were not present before the 9c2 update, and they have noticeably affected the drivability of the vehicle. It was suggested the transmission needed time to "relearn" driving patterns, but it has been several weeks with no change.

On June 22, my 2015 Hyundai Sonata suddenly lost all electrical power without warning. The vehicle stalled and would not restart. There were no warning signs beforehand. After the incident, the car had no electrical power and was inoperable. Further inspection determined that the engine had failed and required replacement. I maintained the vehicle with regular oil changes and was unaware of Hyundai’s service campaign 953 (ksds update). I was never notified that this campaign needed to be completed, and I believe that failure to receive notice contributed to Hyundai’s denial of my engine replacement claim. I purchased the vehicle December 19, 2019. I was never notified by the dealer or manufacturer.

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.

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).

My Hyundai Sonata engine stalled out while driving on the highway. I had it towed to a dealership with the hope they would fix the issue because it was supposed to be covered under warranty from a recall. The dealership said the engine replacement would be covered as long as they got approval from Hyundai. Hyundai apparently only asked that specific dealership for the service records that they had, didn’t even reach out to me or try to find any other service records on the vehicle and denied the claim for “neglect of maintenance” because that dealership only had records from 0-90,000 miles. The dealership got back to me and told me the news and I told them that I will get all service records from 0 miles to current. I got all those records together and sent them to the dealer. A week later they called and said Hyundai was again going to deny my request because of the same “neglect of maintenance” which isn’t true based on the records I have and they have. I have driven the vehicle less than 10,000 miles and there has been nothing wrong with it. No check engine lights ever and regular oil changes.

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.

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.

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.

The engine failed due to the known recall defect, dealer confirmed loss of compression in cylinders 2 & 4. I am a federal employee stationed overseas on official duty orders, and Hyundai motor America is delaying safety recall remedies and buyback negotiations since June 9th.

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!.

I have the 2015 Hyundai Sonata with the 2. 5 gdi engine that eventually will seize due to internal damaged caused by manufacture design flaws. My Hyundai threw a p0010 code which causes my car to idle high and causing low vacuum affecting my brakes. I had a diagnostic test done at a Hyundai dealership that told me it was a cvvt cam sprocket issue and that it was the beginning of the end of the engine, they quoted me 3700. 00 but the engine was to far gone and this repair would only accelerate the engine to seize. They said since the engine isn't seize Hyundai will not cover the cost to repair or exchange the engine, I contacted the Hyundai customer service who stated since the repair that is needed wasn't the root cause of the problems associated with the engine swap warranty they were not going to help me even though I explained to them that the cars high accelerating and the braking system been jeopardized and been told the engine is beyond repairs I feel Hyundai should reconsider their decision and help a loyal customer. I have purchased 12 brand new hyundaj since 2001. The customer representative was extremely un professional even suggesting I scrap my car, also I contacted my Hyundai service technician who said Hyundai customer service never contacted them about my car, when they said they spoke with the technician. Also I received an extended warranty on the 2. 4 gdi engine from Hyundai who many Hyundai customers are or have dealt with. I also purchased an extended warranty which I believe should have been extended as well thank you.

Since I have owned this car they have replaced the knock sensor twice. There is a recall on the engine for crank bearing wear, my car now is burning through 5 quarts of oil every 2 weeks with no oil leak spots on the ground. I would like them to replace the engine as per the recall. The knock sensor should be an indication of the bearings going bad. I have been getting the run around from the dealer in salem, oregon. So, I would like some assistance with this problem thank you for your time.

Car stopped on the road last week 4/6/26 could not start had to get towed mechanic says no oil in engine received oil change last month.

My vehicle has a lifetime warranty that is currently not being honored. It is currently in limp mode and showing a code p1326 which is an engine failure and possible fire hazard. The dealership has had my car for three weeks and have made no attempts to repair my vehicle which they are required to do by law under the theta ii settlement. I was lied to by both dealerships. One stated my vehicle was branded as junk which was false. And now they are denying me due to mileage which shouldn’t be factor since the warranty is a lifetime warranty.

My engine is a class action lawsuit and Hyundai refuses to honor their extended warranty because my title has a brand on it. (odometer issues) my car has been a the dealer for a month and Hyundai refuses even though it's a safety issue and a defect in their design. I want a new engine. The car is perfect otherwise.

The incident began following a routine maintenance visit on March 16, 2026, and has been a continuous, ongoing safety hazard every single day since. While the vehicle was in for routine brake service and an oil change, the dealership automatically applied an open, manufacturer-mandated ecu s/w update theta ii (26-01-013h-1) under service campaign 9c2 emissions (code np001-sc9c2) without my prior knowledge of its drivability side effects. This software flash directly compromised the vehicle's powertrain logic, creating two notable, daily safety failures. First, within the first 5 minutes of engine startup, and most pronounced on every cold engine startup, the throttle delivery is highly erratic, causing uncommanded low-speed surging. In a specific incident in a parking lot following a cold start, I accelerated to approximately 15 mph and completely removed my foot from the accelerator pedal to coast. Instead of slowing down, the vehicle unexpectedly lunged and pulled ahead forcefully against my intent. Second, even after reaching full operating temperature, the vehicle completely loses safe and predictable engine braking at greater speeds; when lifting off the gas pedal, engine rpms aggressively drop, causing the vehicle to coast freely as if in neutral. Re-applying the accelerator causes a violent "phantom shifting" downshift and a hard transmission lockup. My safety and the safety of others are put at risk every time the vehicle is driven. The low-speed throttle surging creates an ongoing risk of hitting pedestrians or cross-traffic, while the permanent loss of predictable engine braking drastically extends stopping distances. No warning lamps or diagnostic trouble codes (dtcs) appeared prior to or during these continuous failures. The vehicle remains available for inspection.

Rod bearing failure.

The contact’s daughter owns a 2015 Hyundai Sonata. While driving and coming to a stop, the vehicle lost motive power. There was no warning light illuminated. The vehicle was towed to the dealer where it was diagnosed with engine failure. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. The dealer informed the owner that the failure would not be covered under warranty due to a lack of engine maintenance on the vehicle. The owner provided the maintenance records. The manufacturer was made aware of the failure, and a case was opened. The failure mileage was approximately 124,000.

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

The bearing failure from the metal debris had been progressing silently for a long time. You can’t feel or hear it happening gradually. Then at some point the damage crosses a threshold where: ?the oil can no longer circulate properly ?the crankshaft bearings completely fail ?internal metal parts make contact with each other ?everything locks up instantly.

Federal report on technical obstruction and warranty fraud (theta ii settlement) national highway traffic safety administration (NHTSA) from: [xxx] VIN: [xxx] repair order (ro#): xxx vehicle location: Hyundai shop - [xxx] Hyundai corporate case: #xxx state complaint (az ag): xxx I. Chronology of events and evasive tactics all documentary evidence has been formally submitted to Hyundai motor America’s national consumer affairs department, addressed to case manager bryan, at [xxx] and via the official email: [xxx] . Step 1: falsification of title status (code a99) Hyundai initiated its denial by alleging that the vehicle held a "salvage" title status, citing internal code a99. Evidence: I possess a certified and stamped motor vehicle record (mvr) from the arizona mvd, as well as my clean title. Mr. Bryan categorically asserted that code a99 "cannot be removed," thereby deliberately disregarding an official state certification. Step 2: allegation of negligence (karen) corporate representative karen claimed via telephone that the vehicle's failure was attributable to "negligent maintenance. " evidence: the official webdcs report—printed by mr. Ismael barragán (service drive manager)—completely refutes this claim; the blue link service history indicates "0 findings. " step 3: fabricated diagnosis and breakdown of improper charges after being compelled by mr. Bryan to take the vehicle to the dealership for a diagnosis, the narrative shifted to an "oil pump failure. " mr. Ismael barragán (service drive manager) presented a billing estimate to the customer under repair order (ro) #xxx, itemized as follows: mechanical diagnosis: $193. 00 usd engine replacement/rebuild: $11,980. 58 usd total demanded from consumer: $12,173. 58 usd technical emphasis: the blue link report (showing 0 findings) serves as irrefutable information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

I was driving on the highway and the engine shut off but everything else remained on. I drifted to the breakdown lane and turned the car off. It would not start again and the car began acting up by turning lights on and off, telling me to check the tire pressure, and not unlocking the doors. I then saw some very light smoke from the engine compartment. I popped the hood and looked and saw a glow on the bottom side of the engine area. Then the car just went up in flames.

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

Was driving car and it went completely hot. Towed to a dealership and they said was not drivable and that the radiator support and radiator hose needs replacing and eventually the drive cv left and front will need replacing or I will be stranded on side of road.

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.

Engine completely seized while driving.

The car is burning a quart of oil a week.