Which parts fail
Components named in complaints (battery, alternator, wiring, ignition, instrument cluster, infotainment).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2018 Kia Optima owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2018 Kia Optima. The contact stated that the vehicle was sputtering while being started. The contact stated that the vehicle also sputtered while driving at various speeds, and while reversing. The check engine warning light was illuminated. The vehicle was taken to the dealer and the contact was informed that oil was getting onto the spark plugs and ignition coils. The spark plugs and ignition coils were replaced; however, the failure persisted. The manufacturer was not made aware of the failure. The approximate failure mileage was 70,000.
Was driving on the interstate. The only light on was the ABS light and the car started smoking. Had to come to a stop as they were sparks coming from out under the car through it into park at around 15 mph steel jumped out of the car and within a minute the car was fully engulfed in flames.
My cars bulbs have been blowing on a regular basis for two years..some of the bulb connections are catching fire and exploding .Ive changed on numerous occasions but doesn't matter even with new fittings...obviously an electric problem
While driving, car in motion, Front Passenger Seat belt Audio Warning Periodically goes off without reason. Indicating seat is occupied & seat belt needs putting on. When seat has been unoccupied / clear from any type of weight on seat to trigger sensor. Audio warning will continue until seat belt is latched over the empty seat. Local KIA Service Dept was informed & could neither confirm or deny its faulty behavior for it did not present itself during time of service. They said, wiring looked fine but did no further testing. To be honest they showed no interest into seeing any real importance for my concern for them to feel any further investigation was warranted. Its happened again twice since that service visit be it last incident Aug 7th. My concern is.... …
On August 26, 2025, I brought my 2018 Kia Optima Plug-In Hybrid to an authorized dealer for recall SC218 (engine inspection and KSDS software update). The dealer verbally stated both SC218 and SC278 recalls were completed, and the repair order (RO #[redacted]) lists them as performed. In September 2025, Kia America emailed me showing recall SC218 still open, and a warranty coverage report dated September 26, 2025, again listed SC218 as unclosed. On November 4, 2025, NHTSA's official VIN lookup confirmed the recall remains "Incomplete." On October 21, 2025, Kia America emailed me under Case #[redacted] stating that SC218 was "confirmed completed" and that the dealer performed a software update to the ECU, referencing RO #[redacted]. However, NHTSA's database still lists recall SC218 as incomplete. …
I turned the car off, it had difficulty turning back on and the brake pedal got really hard. I had to wait about 30-45 minutes and then I was able to get the car started and brake pedal back to normal and no lights. Recently, I left the car on to run into a shop real quick and come back out. When I got back to the car, the power steering light, battery, and warning light?(amber triangle with ! In the center of it) were all on. I rev the engine and the issue went away for a quick second but then came back on. To avoid turning my car off and being stuck, I just shift to reverse and tried to leave. I'm backing out of the spot and now the backup camera is going in and out lights flashing on the dash and I'm trying to brake but the brake pedal isn't registering and next thing you know, I've backed into a guard rail. …
I am submitting this complaint regarding ongoing and persistent mechanical issues with my vehicle since the time of purchase. The vehicle has repeatedly shut off unexpectedly, creating a serious safety concern. Initially, I suspected the issue might be related to the battery, and I have replaced the battery twice within the past 4 years. However, the problem has continued. In January, the vehicle began shaking and shutting down again. I took it to a mechanic, who diagnosed the issue as faulty spark plugs and an ignition coil. The diagnostic codes provided were P0303 and P0456, and the recommended repairs were completed. Approximately one month later, the vehicle began shutting off again. I then took it to the dealership, where I was advised that the valve cover gasket needed to be replaced, along with the belts, and that a fuel system cleaning was required. …
There is already the theta 2 campaign on my Kia optima but Kia is not upholding their warranty for a new engine. Kia customer care told me that untill my car actually throws a rod then they will not fix it. So I could be doing 80 down the freeway and jeopardize not only my safety but everyone else's for them to uphold their lifetime warranty? Also upon doing further investigation and I don't know how many cars this pertains to but the fuse box in my 2018 actually belongs to a 2016 which if you look it up yes they are comparable but don't offer all the same functions or power that my 2018 needs to run I fully believe Kia knew this when they were being built on the factory line because it just so happens that there is about 6 different versions to the pcb relay that can fit from a 2016 to a 2020 k5 but for some odd reason every car got something different why?
The headlights on my 2018 Kia Optima have been turning off and on randomly by themselves while in motion. Each time it's happened has been in different areas at different times of the night. The headlight switch is kept in the auto position most of the time. When the headlights turn off, the screen in the dash for the headlight function switches from auto to off by itself. Sometimes if the turn signal switch is jiggled the lights will come back on. Other times the headlight switch, located on the end of the turn signal switch, has to be turned to the on position to get the lights to turn on. The car has been in for service but each time the technician is unable to reproduce the fault. It is occurring more frequently and becoming a safety issue.
Me and my family just returned home from the laundry mat and took 2 children inside our house and turned around for our belongings and clothing/bedding for the family as the wheels spun out being followed by a silver hyundaii. Just a matter of seconds to 2 minutes. The keys were not in the vehicle. 2 childrens carseats and almost ALL of my family's belongings were stolen inside of the vehicle. 2018 kia optima dark slate grey in color with dark tinted windows and sun strip at the top of windshield, black rims. CR 21077 IL LICENSE PLATE This seems to be an ongoing issue with kia and hyundaii vehicles being stolen and somehow im still not being offered a loaner vehicle with full coverage insurance
Electrical complaints in other Optima years
Frequently asked questions
How common are electrical problems on the 2018 Kia Optima?
NHTSA has 33 complaints about the electrical system of the 2018 Kia Optima, 14% of the model year's 232 complaints. The component named most often is ignition › coil › spark plugs (2 mentions).
Is there a recall for 2018 Kia Optima electrical problems?
No. NHTSA lists no electrical system recall for the 2018 Kia Optima, though it has 2 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2018 Kia Optima electrical problems start?
Half of the complaints with a recorded mileage happened before about 42,000 miles, and 38% before 25,000 miles.
Is it dangerous?
Owners linked 0 crashes, 2 fires and 0 injuries to electrical system problems on this model year. If you notice symptoms, have the car checked before driving further.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.