2018 Kia Optima Electrical System Problems

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. I subsequently had these repairs completed by my mechanic. Less than a week after completing those repairs, the vehicle once again began shutting down. A diagnostic scan then produced code P123300. In addition to these repeated shutdowns, the vehicle consumes an excessive amount of oil, has poor acceleration, and continues to stall unexpectedly both while driving on the road and while idling, such as in a drive thru. These recurring issues have made the vehicle unreliable and unsafe. I am concerned about the risk of the vehicle shutting off while in motion, which could lead to a dangerous situation. I am requesting that this matter be reviewed for potential defects or safety-related concerns.

I was sold an unsafe vehicle at J and J Auto house 6446 Wilshire Bl LA,CA 90022. Dealer withheld condition of car . Had car three months and was stranded on highway. Car was towed to Kia dealer and diagnosed with complete engine failure. Dealer will not honor limited warranty, shady sales practices withheld recall info during sale, won’t allow his mechanic to look at car, dodged calls, denied request to return car for refund

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. On the way to drop my kids off at the babysitter, I was coming to a stop sign, and my car wouldn’t brake, i went through oncoming trafic and had to run off the road. KIA did a multi point inspection a few months apart from one another. One the car tested fine, then the second time they are saying a brake booster and no engine oil in the vehicle and that the car is basically trash. The oil light goes on and off and I can smell burning oil. I still owe 7 grand on this car and I just bought it last year and it was seamingly fine.

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 #XXX) 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 #XXX stating that SC218 was “confirmed completed” and that the dealer performed a software update to the ECU, referencing RO #XXX. However, NHTSA’s database still lists recall SC218 as incomplete. This contradiction between Kia America’s internal record, the dealer’s invoice, and the federal NHTSA database raises a serious safety concern that the recall inspection or software update was never actually performed or was never reported correctly. I have requested written proof and diagnostic data (Battery SOH report) multiple times but have not received them. If accurate, this means I was led to believe my vehicle’s engine-safety recall had been repaired when federal records still list it as open. I am requesting NHTSA to review this reporting discrepancy, ensure Kia America and the dealer produce verifiable proof of completion, and confirm that the federal record is corrected. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

The car is literally burning through oil so bad every other week I am putting more in, the electrical system continues to fail and shorts, the motor sounds like it is ticking now due to the oil consumption.

While driving at night if the headlights will randomly turn completely off

Oil pressure switch faulty only has 58168

In case of a vehicle lockout and keys are locked in the trunk when car is opened by locksmith there is no way to unlock the trunk from inside of the car the locks become disabled and you have to reset the master switch very inconvenient for emergencies. There is no trunk release or emergency Button to open the trunk from inside the vehicle. 2018 kia optima lx

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.

Engine is burning oil at a high rate have to add at least three quarts twice a week and headlights and brake lights got out twice a month

The engine consumes all the oil within 1000 miles. The oil light comes on around 800 miles after oil change. The dealership did the 3 separate tests and they all failed. Dealership stated the engine is faulty however Kia corporate denied the claim. There is already a class action lawsuit in progress in California.

Normally, when the doors are open my car will tell me. The doors notify me that they're open but my trunk was not showing that it was open. It blinks when it is. Due to that I was driving and my trunk seemed closed and it just flew open. So the problems I'm having is that my trunk will not show its open but it also will not close AT ALL due to the latch. I literally had to bungee it closed. This is dangerous. I have seen many recalls in other kia's and hyundai's just like this. This is very dangerous and needs to be recalled and/or fixed.

Rough idle, chugged along before killing engine power. Has happened a couple of times. No check engine light has come on

When headlight switch is set to automatically come on, the light will sometimes randomly turn off. No warning or indicator on the dash appears showing that they are off. Technicians are unable to reproduce the issue in the shop. Have recommended replacing the entire headlight switch on the turn signal stick.

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

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.

My car has been at the dealership since February 10th. The dealer has been giving me the run around. Didn’t have any transportation for over two months and car hasn’t moved since the day I dropped it off. I’m really getting impatient, as I am making monthly payments on a car that I can’t even use. Nearing four months and I’m totally lost on what to do. Thank you for any assistance

Vehicle is making a noise when trying to accelerate. Have replaced all spark plugs and coil #4. It is making noise still and shaking. Coil has been switched and issues are reading fuel injector or air intake or electrical. Previous reading was head gasket... Only on spark plug 4 coil is it reporting an issue...All dealerships locally are booked to even get a diagnostic test.

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.... if there is faulty wiring or sensor signals being crossed somewhere, whats to say there is a passenger or no passenger in that seat, to ensure the correct signal is getting to the passenger side air bags of when to correctly deploy if an accident should happen with passenger in seat? This situ is only recent starting about a year a go. So something has changed from being fine for 2 yrs up to the last year that's now showing some kind of seat belt / sensor failure. I'm unfamiliar with how that wiring system works & linked within it for me know what other things I might need to pay more attn to, looking for other signs that could be saying is direct cause to the prob. Unsure if this a simple solution or is something that others are experiencing with this year & model car & poss be a Manufacturer Part Default

The electrical components connected to the headlights seem to be faulty. When lights are set to AUTO, the lights will turn off completely when switching on turn signal. At times the light will not come on at all when set to AUTO or On without cycle back to off.