Owner-reported complaints naming the powertrain system, filed with NHTSA
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Powertrain reports that are not specifically the engine or transmission — driveshafts, axles, transfer cases and differentials. Every record below is an owner-reported complaint about the 2015 Kia Optima submitted to NHTSA — not a confirmed defect, not a recall and not a manufacturer bulletin. 48 reports on file name it.
Complaints are reports submitted by owners and drivers to NHTSA. They are not verified and do not establish that a defect exists.
The 25 most recent of 48, in the owner's own words
P1326 code flashing engine light knock sensor went out 3 times in 6 months and just replaced it again and this time engine light didn't go off I was reading that there was a recall on this but apparently mine doesn't state it. Car cannot pass emissions if engine light is on and the 15th of June is approaching. The car doesn't make any sounds or nothing.
On December 27, 2025, at approximately 150,556 miles, my 2015 Kia Optima Hybrid experienced sudden engine knocking, power loss, and failure while driving at 65 mph on a highway. The vehicle dropped into limp mode and I had to pull off the highway. The car required towing to the dealership as it would not drive safely. Diagnostics revealed a knock sensor error (P1326 code) and failing connecting rod bearings via Bearing Clearance Test, consistent with the known Theta II engine defect (manufacturing debris causing oil starvation and premature bearing wear). This follows earlier symptoms: Intermittent 'Check Hybrid System' warnings in early December 2025 at 148,665 miles (dealership unable to reproduce, but historical codes noted). The Knock Sensor Detection System (KSDS) software update was performed in February 2022 during prior CHS warnings. Despite onset of issues under the 150,000-mile extended warranty limit per the Kia E2 Settlement, Kia denied coverage due to the minor mileage overage and directed me in a loop between Consumer Assistance and the Settlement Administrator. The defect poses a serious safety risk: potential for sudden engine seizure, stalling while driving, or engine compartment fire (as seen in related Theta II recalls and thousands of NHTSA complaints). No crash, injury, or fire occurred in my case, but the failure left the vehicle undrivable and unsafe on the road. I have service records and diagnostic reports to support this.
While driving my 2015 Kia Optima (VIN: [XXX] ) at highway speed, the engine suddenly shut off without any warning lights, alerts, noises, or check-engine indicators. This created a dangerous situation for me and surrounding drivers. The vehicle had passed state inspection only 3 months earlier with no issues. The sudden shutdown is consistent with the known Theta II engine defect investigated by NHTSA. The car is now completely undrivable. Two Kia dealerships refused to assist, claiming that they cannot perform KSDS because the engine is already dead. These reasons directly contradict the Kia Theta II engine settlement terms. This sudden stall is a safety hazard and could have caused a severe crash. I am requesting that NHTSA review this incident as a potential recurrence of the engine-stall defect already documented in Hyundai/Kia vehicles. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)
Vehicle experienced sudden loss of power while driving when cylinder 3 completely failed (0 PSI compression). Metal particles found in oil and excessive oil consumption (1 pint/100 miles). KIA dealer diagnosed as piston rings but ignored metal in oil that suggests bearing failure covered under recall campaign. Refused proper diagnostic testing. Vehicle now unsafe to drive with failed cylinder that could cause complete engine seizure while driving. Kia had all recommended services and oil changes since acquired in 11/2016. These service records demonstrate the progression of my vehicle's engine issues, from early oil consumption problems documented by York Auto Care in July 2023 (3 quarts low) to complete cylinder 3 failure with zero compression confirmed by Kia's own diagnostic testing in May 2025. Despite this documented history and Kia's own test results showing catastrophic engine failure, they have denied warranty coverage under their engine campaign that specifically covers bearing-related failures on my 2015 Kia Optima 2.4L.
My 2015 Kia Optima Hybrid poses a serious safety risk. While driving at highway speeds, the car has randomly shut off multiple times. A "Check Hybrid System" or hybrid battery warning appears on the dashboard, and the vehicle either loses power entirely or switches to electric-only mode and coasts to a stop. This happens without warning, putting my life and the lives of others at risk. I already had the relevant hybrid system recall work completed by a Kia dealer, but the issue persists and the car remains unreliable and unsafe. This appears to be a known issue affecting many 2011–2016 Optima Hybrid vehicles. Kia needs to be held accountable for continuing hybrid system failures that occur post-recall and outside of warranty. This is a dangerous, recurring defect.
Was driving down the highway and all of a sudden the car shut down in the highway lucky cars was not close by. Tried to crank it it would not crank would not take a boost it won’t say anything I had the battery checked at auto zone the battery is really good. The mileage on the Kia optima is 1,900 actual miles it will not crank or move it was very scary I called Kia customer service there wanted to charge me over $400.00 dollars to come get it and take it to the shop so it took me 2 days to find a tow to get it home and it still needs to go to the Kia shop
The contact owns a 2015 Kia Optima. The contact stated that while driving at various speeds, or while at a complete stop, the vehicle would shut off without warning. The vehicle would resume normal operation upon restart of the engine. The vehicle was taken to a dealer for an inspection; however, the dealer was unable to duplicate the failure. The manufacturer was not notified of the failure. The vehicle was not repaired. The failure mileage was approximately 88,000.
Engine locked in while driving on road No power an won’t start
Driving one day in Dec 2021, and there was a hybrid system warning and vehicle suddenly stopped on the road. Called tow truck. We were unable to put the car in neutral to tow. Had tow truck deliver to dealership for diagnostic and repair. Dealer replaced transmission and stated it was covered under warranty. Finally got vehicle back and warning still pops on dashboard. We’ve taken it back several times and warning randomly appears. Dealership unable to recreate the warning to diagnose. Unable to drive the vehicle over long distances due to safety concerns.
I NEED REMEDY COMPENSATION IN REGARDS OF MY RECALLS MY ENGINE WARRANTY WAS GONE AFTER BEING REPLACED DUE TO ENGINE SEIZED 01/01/2023 I HAD ENGINE WARRANTY SINCE 2020 AND NOW MY CAR WAS BEING REJECTED REFUSED REJECTED EXCLUDED IAM BEING DISCREDITED I OWN MY 2015 KIA OPTIMA I LIVED SLEEP IN MY CAR IAM HOING THROUGH FINANCIAL HARDSHIP SINCE 2021 I NEED LEGAL ADVICE HELP ASSISTANCE PLEASE
The vehicle has a seized motor within the manufacturers powertrain warranty. They are denying to repair/ replace the motor because they claim a recall was not performed. The NHTSA does not currently show the recall that needed to be performed. The vehicle should still be covered by KIA's powertrain warranty and the dealer is not accepting responsibility.
1. While stepping on the brakes my car has revved up as if I was pressing the gas. So I let my foot off the pedal and pressed the brakes again. This happened 2 times that week. And another time while I was coming to a stop light as I pressed the brakes, my car revved up but didn’t actually make my car speed up. I had to press the brakes again for it to stop. 2. My battery was smoking and I replaced it. 3. My car is consuming oil. The dealership did a series of oil consumption testing due to the exhaust leaving extra carbon residue on my car. They said it was fine but I don’t think they solved the issue.
My car is dragging/hesitant to pick up speed. While on the highway, it takes a while to reach minimal speed. No warning lights are on, but one mechanic advised code, under turbo boost. My steering wheel vibrates at speeds above 40 mph (unsure if it's related to turbo), but no one seems to be able to find the core of the problem for repair, Kia dealership included. I've been trying to seek repair for close to a year, without satisfaction.
My 2015 Kia Optima EX with 56,462 miles which I am the original owner. On 09/07/2024, my vehicle oil light came on and the vehicle was taken to Weston Kia in Gresham, OR. This vehicle has had regular oil changes every 3,000 miles since purchased performed at Weston Kia. The service department found a leaking oil pressure switch and preformed the repairs totaling $248.60 on 09/08/2023. Per Kia 10yr/100,000 Powertrain warranty for original owner "In the Engine: Cylinder block, cylinder head and all INTERNAL PARTS, timing gear, seals and gaskets, valve cover, flywheel, OIL PUMP, water pump and turbo charger, pg. 6." I believe this part is covered per Kia warranty and the definition of drivetrain "A powertrain is a system inside a vehicle, in a car, a powertrain consists of the engine or motor and its internal components, such as the energy storage system, transmission and driveshaft." After reviewing all Kia warranty information and speaking to customer service at 800-333-4542 (Who stated the repairs are not covered), there is no information to the contrary that a oil leaking pressure switch that is located within the engine block is not covered. Kia would not provide any detailed information that shows this part falls outside of the terms of my 10yr/100,000 mile warranty.
The contact owns a 2015 Kia Optima. The contact stated while driving at an undisclosed speed, the brakes and the steering column were inoperable. The contact stated that several unknown warning lights were illuminated. The contact was able to safely pull off to the shoulder of the roadway. The contact stated that the engine started smoking. The vehicle was towed to an independent mechanic. The vehicle was not repaired. The contact stated that in December 2020 and March 2023, recall repairs were completed on the ABS and TCU modules. The manufacturer was made aware of the failure, and a case was filed. The approximate failure mileage was 94,700.
I HAVE 2015 KIA OPTIMA GREY OR PLATINUM GRAPHITE EXTERIOR COLOR SINCE AUG 2019 I HAD AN TBONE ACCIDENT LAST DEC 26 2021 WHICH IAM NOT AT FAULT FOR NEVER RECEIVED ANY TYPE OF COMFORT CARE CLAIM IT WAS DURING COVID PANDEMIC I WAS IN THE PROCESS OF GRIEVIANCE BEING HATE LEFT IN DESPAIR ALSO JOB LOSS WITH NO INCOME UNSTABLE LIVING SITUATION WHICH I WAS LIVING ON MY PERSONAL VEHICLE BEEN GOING THROUGH FINANCIAL HARDSHIP UNTIL PRESENT I HAVENT BEEN DRIVEN UNTIL I BROUGHT TO KIA DEALERSHIP JAN 1ST OF 2023 DUE TO MY PERSONAL INJURY AND CAR ACCIDENT IT WAS LEFT PARKED GOT TOWED WITH BUSTED WINDOWS HAD MY PERSONAL BELONGINGS BEING GONE MISSING.... I HAVE ROUGH YEARS... IT WAS DIFFICULT FOR ME TO GET BACK UP IN MY FEET MY CAR HAS RECALLS ARENT BEING REPAIRED FAIRLY. THIS WILL BE MY FIRST TIME TO ADHERE MY CONCERNS I WOULD LIKE TO GET SOME ASSISTANCE IF POSSIBLE...I THANK YOU IN ADVANCE
Driving on highway at 65 mph and engine just died with no warning. Almost got hit trying to get off the expressway to the side of road. Had car towed home and checked engine. Engine is seized up completely.
Was driving down the interstate and engine cut off suddenly. Had to coast across several lane to pull over out of traffic. This was very dangerous. Had car towed home. Engine is locked up . Called Kia dealerships near me. Closest one is not accepting any engine replacement appointments at this time and don’t know when they can. Wouldn’t even give me a future appointment. Kia lawsuit website says my vin number is covered for engine replacement but I can’t get a dealer to even look at it.
1.Since 1/17/23 I've had 5 occurrences of the car yanking me to the left as I am turning right. The steering wheel gets stiffed, the dashboard lights come one, car slows down and I have to park the car and turn it off and back on. When I turn it back on, no dashboard lights are on and the everything is back to normal as if nothing ever happened. I have taken the vehicle to the dealership 3 times for a diagnostics and nothing comes up. The vehicles computer is not even tracing the times the dashboard lights have turned on as it shows zero history and that is not the case. I have taken pictures and video of the dashboard lights and have showed the guys at the dealership but since there's no record on the dashboard computer/history, they're not able to determine the problem. 2.My safety has been put at risk as I can get involved in a car accident and involve others safety at risk as well. The vehicle doesn't give any prior signs when it's going to act up when turning to the right, therefore it can happen at any given time. The first time I was leaving a parking lot and it happened on the freeway feeder. I towed my vehicle to the dealership the first time as I was in fear of driving it only to be told they can't find the issue. 3.The dealership has ran 3 different diagnostics on 3 different occasions and nothing comes up. It is still unresolved. 4. Kia service department has inspected in on 3 different occasions since the first incident. 5. No warning lamps or warnings of any sort before the first incident.
Knock sensor replaced due to engine knocking did not fix the problem the cars engine does not work it julks and pulls really hard engine noise check engine flashing left me stalled on the main highway with my 2 children with no warning the car has engine oil to adequate levels maintenance was up to date
The engine lost power taking off crossing a major roadway, resulting in a stall, vehicle had to be restarted in a panic. The knocking and loss of power put me and my passenger in danger of a side impact from cross traffic. The issue was reproduced by a dealer upon further inspection. The vehicle will be inspected by a service department at certified dealership. No warnings lights or fault warnings appeared related to this issue.
On 3/1/23 on my way home from my which the site was in Perth Amboy, NJ. At the North Somerset rest stop, just exited the I-76 westbound. I lost power around 65 mph. I didn't get any response from my brakes at first and nothing from my accelerator. Upon drifting and praying that I'd make it to the lot out of the main exiting lane. Upon pulling into a spot at the very farthest spot from the building, I noticed my check engine light is flashing. Press my brakes were working. Accelerator was hardly responding. I've worked on my car and my families cars, and cars most of my life. I had my code reader with me. Plugged it in and got the code that I've heard and read about. P1326 knock sensor. Knowing about this about Kia and Hyuandi, I knew my engine was dead. Thank God it didn't catch fire like some others have. I had it towed to Smail Kia in Greensburg, PA. That was the closest and NOT the dealer I bought it from. We bought it from Century 3 Kia West Mifflin, PA. After their promises that the engine would get replaced, lack of communication, many of my calls,voicemail, emails and showing up in person,(had to move 2 things that would've been in the way of the swapping of the engine) and a week later Kia denied my replacement due to "power adders". None of which I have, use or cause any issues. NO TESTING WAS DONE ON WHAT THEY THOUGHT WAS POWER ADDERS. HOWEVER, ALL OF THE TESTS THAT SHOW THEIR FAULTY ENGINE COMPONENTS AS PERR THE FEDERAL LAWSUITS AND RECALLS.....ALL FAILED! I can't drive the car. It's dangerous for myself and any other motorist. Could explode, catch fire or completely fail on ANY highway/roadway. I need my car for my career and above all, my life sustaining health and medical appointments Now I'm left with no vehicle. I still owe around a year- year and a half. As well as car insurance. Now what? Kia needs to do the right thing here, for myself and anyon else suffering from this horrific life changing nightmare.
August 6, 2022 on Kansas Turnpike near El dorado. 2015 Kia Optima LX 74,000 miles. With absolutely NO warning whatsoever revved high then began a knocking sound, then a horrible banging and died. No lights, no alarms. Steering became a problem. We were able to drift to the side of the road as we were already in the right lane. Once completely stopped dash lights came on. We had no idea of any recalls or issues. Engine never recovered and we procured roadside assistance. Waited 4 hours on the side of the turnpike. We have since learned of a class action lawsuit against Kia with this very issue. We are still waiting for an engine replacement/rebuild 15 weeks later!
2015 Kia Optima Hybrid HEV system. Months after purchasing the vehicle two different lights would come on the engine. One is the HEV warning light and the other is a flashing “Turn off engine and check HEV system”. The first time it happened the vehicle turned off. It was towed to Kia, 02/2020. They change some sensor and sent me on my way. 3 weeks later the HEV warning light came on again so it was towed to Kia for the 2nd time, 03/2020. This time they said they could not recreate the issue. A month later the light came on again and again but since the light never stayed on, I kept getting told by Kia that I’d have to take it in when the light stayed on. 01/2021 the light came on again, with the flashing warning and the vehicle turned off, mid-drive. It was towed to a mechanic shop near me, where they replaced the wiring harness completely, but a month later the same light came on again. Over the course of the year, the warnings kept turning up and time and time I kept getting told they needed the light on at the dealer so they could determine with the codes, what is wrong. 07/2022, light came on as I was merging on to the freeway and the car shut off. I was able to make it turn on and make it home safe. The next day I towed it to the shop where they replaced the wiring harness and they stated they could not touch it further since the codes they got where “High voltage battery” codes and a specific tech is the only one when could work on it. I took it to Kia where it stayed 33 days. They changed a part. Two days later the HEV light came on again, so I took it back. They kept it one day, drove it 60 miles and they could not recreate the issue. I got it back on Saturday, 5 miles out the light came back again and again. I took video. Called Kia and now the car is back at the dealer while they try and figure out the issue. I’m scared for my life. The car gives no warning when it decides to shut off. Wheel locks on the times it does turn off. HEV system is no good.
For one my car is very sluggish when taking off and shifting gears Jerks badly. MY electrical is messing up on my radio and camera. Sometimes I smell rubber burning. When I have my cruise on it will speed up on its on and jerk when it does and when i press my brakesbto slow down it doesn'twant to slow down unless iash really hard. When taking off from a hill or a dead stop it doesn't want to shift and slags and rattles when it shifts. Bluetooth works sometimes and sometimes it doest it depends on when my backup camera works or not. I bought this car used in June of 2021 with a little over 92000 miles. I know when something doesn't sound right and when something is messed up, there is something wrong with my car. So far I haven't been in an accident but I don't want to be either.
Higher-selling and older vehicles accumulate more reports. Counts are not failure rates and are not directly comparable between vehicles that sold in very different numbers.
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