2015 Hyundai Sonata Powertrain (other) Problems

VEHICLE: 2015 Hyundai Sonata, 2.4L Theta II GDI engine Mileage at time of incident: [ 93k Date update performed: June 2026 Dealer/location where update was performed: Fitzgerald Hyundai Gaithersburg, MD DESCRIPTION OF PROBLEM: After my vehicle received the ECM software update issued under Hyundai Service Campaign 9C2 (ECU Software Update for Theta II Emissions Improvement, TSB 25-01-087H / 26-01-013H-1), the vehicle began exhibiting noticeable jerking/hesitation during acceleration that was not present before. For this vehicle this happens consistently after a cold start then does not happen again.

NHTSA ID

11748280

Incident

Jul 1, 2026

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.

NHTSA ID

11746404

Incident

Mar 16, 2026

Car stopped in the middle of the road , with warning beeps and warning messages on the dashboard saying "Check Charging System" .Engine was still running but even though I did accelerate - car did not move . I put on the emergency lights and turned off the car . Turned on the car few seconds later and was able to drive then but the check engine light was on. Slowly drove back to the home as I was less than a mile from the home. It happened on a local road with speed limit of 35 MPH and thankfully vehicles behind me stopped until I pulled over. Me and and 7 year old kid was in the car at the time of this incident

NHTSA ID

11737092

Incident

May 10, 2026

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

NHTSA ID

11726628

Incident

Feb 27, 2026

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.

NHTSA ID

11718641

Incident

Feb 6, 2026

The engine/powertrain on my 2015 Hyundai Sonata (VIN: [XXX] ) has failed due to extremely low compression in all four cylinders, causing severe misfires, hard starting, loss of power, and intermittent rattling noises, and the vehicle is currently available for inspection at the Hyundai dealership. This failure created a safety risk because the engine hesitates, struggles to start, and can stall or lose power during driving, which could lead to a loss of control or an inability to accelerate in traffic. The problem has been confirmed by both an independent mechanic and the Hyundai dealership, who documented low compression across all cylinders. The vehicle has been fully inspected by the dealership on Hyundai’s behalf after I opened a case with the manufacturer. Prior to the complete failure, the car showed warning symptoms such as repeated cylinder 4 misfires, rough starting, reduced power, rattling noises on startup, and the check engine light appearing several times beginning earlier this year. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11701206

Incident

Nov 3, 2025

Our 2015 Sonata has experiencing Engine failure several times due to excessive and irregular oil consumption. Our family’s safety and the safety of others on the roadway were put at risk as the engine slows, shudders and stalls without prior warning and the check engine light does not come on until the vehicle slows and stalls. The vehicle was inspected at a local Hyundai dealership, and they indicated that this is not covered under warranty. Summary of Engine Issues and Failures: 1.May 3, 2022 – 68,671 miles (local Hyundai dealer) Check engine light on, shudder; oil change performed. No cause identified. Paid out-of-pocket. 2.August 23, 2022 – 75,527 miles (retail shop) Car engines failed on highway, towed to service shop. Valve cover gaskets replaced. Paid out-of-pocket in part and extended warranty paid part of the invoice. 3.April 29, 2024 – 109,229 miles (local Hyundai dealer) Excessive oil consumption noted; valve cover gasket replaced again. Paid out-of-pocket. 4.January 22, 2025 – 118,341 miles (local Hyundai dealer) Vehicle stalled en route to airport, towed to dealership; dealership advised oil change. Paid out-of-pocket. 5.May 20, 2025 – 122,000 miles (local Hyundai dealer) Engine codes P0300, P0302, P0303 identified. Dealer diagnosed excessive oil consumption likely due to ring wear or sticking rings, contributing to spark plug misfires. Recommendation: Engine replacement. Despite consistent and timely service, including multiple visits to the Hyundai dealership, the root issue has not been properly addressed. The current diagnosis of internal engine failure is a clear continuation of a pattern of unresolved engine problems (stalling in motion, oil leaks and oil consumption) all of which originated well within Hyundai’s original warranty. The vehicle has been well maintained, and all recalls have been addressed in a timely manner. Hyundai’s failure to acknowledge and take responsibility for this widely documented engine issue is a safety concern.

NHTSA ID

11669597

Incident

Jan 22, 2025

While traveling on local roads and highways the vehicle transmission randomly down-shifts one or two gears. This has occurred when traveling in any gear from gears 3 through 6. It probably doesn't happen in 2nd gear because that is a transitory gear and not a cruising gear. After quickly moving the shifter from automatic mode into manual mode and then back into automatic mode the transmission returns to the proper gear. However sometimes it has down shifted again in as little as 30 to 60 seconds after resetting the shifter. This has been happening for years. The dealership has been unable to fix it. Because it is random, the issue is not readily reproducible by the repair shop. Sometimes it has happened several times within a 15 minute period. Sometimes it has occured multiple consecutive days. Other times a week or two has passed with no incident.

NHTSA ID

11650171

Incident

Mar 18, 2025

My transmission literally went out once on me the SECOND DAY after I financed it. Now, less than a year later, it says I need to replace the transmission again. This is ridiculous.

NHTSA ID

11613138

Incident

Sep 6, 2024

UNKNOWN, car was driving fine on the highway, then all RPMS were lost and the car couldn't accelerate past 40mph. At the same time a loud knocking started and when i was able to park and pop the hood, the engine was clearly vibrating and the source of the knocking is undetermined. there are recall's for improperly welded rods in the 2013/14 model sonatas and the 2016 so i find it hard to believe that Hyundai doesn't know that this year and make would have the same known issue and those models have all had recalls already except for mine...

NHTSA ID

11592327

Incident

May 27, 2024

I have had my car serviced twice by the Hyundai dealership for the same exact issue. I believe I was told it was a knock sensor. A refurbished engine ended up being put in. The car is still having the same issues as when I first got it serviced in 2021/2022. My car is sputtering, loses power when accelerating and stalling. My car has always had an oil consumption issue and is causing additional issues with spark plugs.

NHTSA ID

11588689

Incident

Apr 30, 2024

While driving our vehicle (Hyundai 2015 Sonata Hybrid) around 25 MPH speed in city road... the vehicle stopped completely by itself in few seconds. Got the message "Hybrid System Warning! Safely Stop and Do not Drive" in dashboard and beep beep sounds. Thank god, no accident, the vehicles behand able to stop and avoid the collision. This is serious SAFETY issue, as this could cause accidents if vehicle stops by itself while driving. This is 3rd time in last few years with this vehicles. The recent incident happened was on 5/1/2024 morning around 8.00 am. We went to the Hyundai Service Center and they did looked at the codes and ran some scans and they found nothing wrong. And they said it could be some wrong system warning and can be ignored, as they can't reproduce the issue. And told us to report if this happens, but the worry is that, if this happens it could be serious life threating accident or injuries. They said they also got similar other Sonata Hybrid got same issue reported same day, but they can't find root cause. Same issue was happened last on 9/30/2022 and one before in that same year. They can't find the root cause that time too. They just updated software that time...and hoped that will fix. But the issue repeated again. While searching on the internet, found many people reporting this same error message and suddenly stopping the vehicle by itself. Very scary safety concern. So that's why we are reporting this to NHTSA. To take action on this with the Hyundai and investigate more. Now worried when we drive this vehicle. I have all pictures taken when this issues happened on 5/1/24 and also 9/30/22. I will share those here. Let me know if you need more information on this.

NHTSA ID

11586683

Incident

May 1, 2024

The car has been having problems with oil consumption. The problem became known in 2022, but the dealer/service department (Frank Hyundai, National City, CA 91950) did not care for the issue or safety. The dealer told me, "Your car is OK." On 7/3/2023, the engine light came on. A second round of oil consumption tests began along with a 90,000-mile service, including replacements of filter assy and gasket, four new tires and front and rear brakes, spark plugs, suspension/steering repair, shaft assy, engine repair, cooling system service, and fuel induction service. Shortly after, the car slows down even when my foot is on the accelerator. It feels like the vehicle will stall/stop (while driving in the middle of the road). I can see the rpm gauge erratically going up and down. The car lurches or jerks. I reported the jerky problem to the dealer at the second 1000-mi oil consumption test, but the dealer did not make any diagnostic tests or repairs because, per the dealer, "it did not jerk while we test-drove it." The problem continues.

NHTSA ID

11562727

Incident

Nov 21, 2022

The car has been having problems with oil consumption. The problem became known in 2022, but the dealer/service department (Frank Hyundai, National City, CA 91950) did not take care of the issue and did not care about safety. The dealer told me, "Your car is OK." On 7/3/2023, the engine light came on. A second round of oil consumption tests began along with a 90,000-mile service, including replacements of filter assy and gasket, four new tires and front and rear brakes, spark plugs, suspension/steering repair, shaft assy, engine repair, cooling system service, and fuel induction service. Shortly after, the car slows down even when my foot is on the accelerator. It feels as though the vehicle will stop. I can see the rpm gauge erratically going up and down. The car lurches or jerks. I reported the jerky problem to the dealer at the second 1000-mi oil consumption test, but the dealer did not make any diagnostic tests or repairs because, per the dealer, "it did not jerk while we test-drove it." The problem continues.

NHTSA ID

11562726

Incident

Nov 21, 2022

When I press on the brake the vehicle accelerate before it slows down. Sometime the car accelerates for no reason. This has been a recent problem for the past few months. The engine has been replaced from a prior recall.

NHTSA ID

11562177

Incident

Dec 27, 2023

Hybrid system warning comes up often and everytime I take it to get assessed, something different is getting fixed. These repairs are all expensive out of pocket repairs. The problems continues to happen and I’m constantly repairing something different.

NHTSA ID

11549889

Incident

Sep 10, 2023

Mileage

162,553 mi

The contact owns a 2015 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, the car stalled and struggled to remain running. The contact stated two days later the vehicle was parked and while hitching the RV to the trailer hitch, the vehicle independently moved and collided with a dolly. The contact stated that the dolly was used to load the RV to the hitch. The vehicle was towed to the dealer. The vehicle was being repaired. The dealer informed the contact that the vehicle could not be diagnosed until the vehicle was repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 60,000.

NHTSA ID

11549762

Incident

Sep 19, 2023

Mileage

60,000 mi

Car stalls intermittently. When at a stop sign or red light, then when my turn to go I step on gas peddle, car starts to go, then stalls. I have to let off gas pedal and step on it again to get car going. This is dangerous as it leaves me in intersection and vulnerable to oncoming traffic. I had a mechanic check it out and they cleaned Throttle body, but that did not fix problem. No trouble codes showing up apparently.

NHTSA ID

11546838

Incident

Sep 26, 2023

Hybrid car with various hybrid system failures that results in sudden loss of power while driving. this has occurred 3 times to me while on the highway (I-75 in South FL). Car suddenly loses power, could not accelerate but I was able to get off the highway safety. This has been reproduced at the dealer and they first replaced the hybrid generator then the hybrid battery and ECM and now it occurred again yesterday while I had 2 children with me and now they blame the transmission. This is a dangerous car that should be recalled and investigated for the true cause of sudden and unpredictable power loss.

NHTSA ID

11544187

Incident

Sep 11, 2023

I would like to write about my experience with New Port Richey Hyundai. I have owned a Hyundai Sonata Hybrid Limited since 2015. I take immaculate care of my car and it only has 65,000 miles. All maintenance has been done regularly and on time. For the last six months I have had a warning light and alarm going off for a few seconds once in a while, which shuts off my cruise control. I took the car in, in the spring of 2023 to have the codes read and no problems were found. Finally, In July of 2023, while my wife was in traffic it started again and totally shut off the car. Unfortunately, the brakes did not work as well. She was going up a slight incline and was able to come to a stop. The brake pedal went completely to the floor. The warning was about a Hybrid System Failure. It was very upsetting to her that her brakes failed when the Hybrid system had a problem. This should never happen! Once the car was towed to New Port Richey Hyundai in Florida, we were told that the car would be look after. The car was returned in the middle of July 2023 with a new electric motor installed. Everything was working fine until today, August 23, 2023. The same warning light that I brought the car in for in May 2023 is going off again. It only stays on for a second or two, so I don’t have time to read it. I really hope this car does not shut off again with no brakes when traveling on the interstate. As mentioned before the car has low miles and is well cared for. This should not be happening.

NHTSA ID

11540349

Incident

Jul 5, 2023

The contact’s daughter owns a 2015 Hyundai Sonata. The contact stated that while the vehicle was idling, the vehicle hesitated. The contact stated that his daughter had to depress the accelerator pedal to rev the engine. The contact then stated that on a separate occasion while driving at an undisclosed speed, the vehicle hesitated and stalled. Additionally, the contact stated that on another separate occasion while his daughter was driving at an undisclosed speed, the vehicle unintendedly accelerated. The contact’s daughter was able to regain control of the vehicle and depressed the brake pedal to stop the vehicle. The check engine warning light was illuminated. The vehicle was towed to an independent mechanic where the vehicle remained. The cause of the failure was not yet determined. The vehicle was not repaired. The manufacturer was not notified of the failure. The failure mileage was approximately 95,000.

NHTSA ID

11540173

Incident

Aug 21, 2023

Mileage

95,000 mi

The engine and yes it is. Because my car turned off in the middle of the loop on the highway when there was a lot of traffic and we could have gotten hit. No it has not been. No it has not been. We were driving on the highway then the engine started sputtering and it wouldn’t go faster then 40 when I tried pulling off to the side that’s when the engine ,battery ,and oil light turned on and after that the car just shut off and wouldn’t want to turn back on.

NHTSA ID

11535396

Incident

Jul 30, 2023

City driving and the bells and warning message on the dash stated the electrical system was being evaluated for causes why the engine/electric drive failed

NHTSA ID

11529258

Incident

Jun 26, 2023

can't use eco sport motor is accelerate and the car can't read the sensors a/c stop working brakes hard to press

NHTSA ID

11526382

Incident

May 3, 2023

2015 Hybrid Sonata, milages at 82,000 km, owned for 8 years. "Hybrid system warning, do not drive" message occurred, car lost 100% of its power, went into complete stop without any warnings on the middle of the highway. Hazard lights do not work and unable to warn incoming traffic that the car has completely stalled in the highway. The car is unsafe to drive. Went to Hyundai (here in Canada) several times, being charged every time for diagnostic and repair works, been told that the issues were fixed via software update. Problem persists. There are compelling evidences from different car forums, websites and NHTSA own database (28 reports under Unknown, 22 reports under Electrical sys. categories...) on the hybrid system failure or/and 100% power lost lead to complete stalled car. Although all these reports did not site any injury, major or death events, NHTSA should compel Hyundai to take appropriate actions to render the car safe to drive for the public because if accidents should happened, it cannot be undone and will affect lives of people. The public relies on a governing body to represent us and hold the manufacturer responsable to ensure that their mkt released products are safe: to save lives, prevent injuries, reduce vehicle-related crashes.

NHTSA ID

11525995

Incident

May 31, 2023