Was driving and stopped at a stoplight. When I went to drive it started sputtering and if I wouldn’t have driven into a gas station, it would’ve given out in the middle of the road. It wouldn’t let me switch to drive or reverse , only neutral or park. It threw a code P0301, cylinder 1 misfire. Had to get it towed. Now I have to get my spark plugs and fuel injectors replaced.

The contact owns a 2023 Hyundai Sonata. The contact stated that while his wife was driving at an undisclosed speed, the message "Engine Overheated" displayed. The contact checked the Hyundai app, but it showed no failure. The contact's wife drove to their son's residence, who inspected and discovered that there was no coolant in the engine. The contact's son added coolant to the engine. The vehicle was taken to the dealer, who replaced the coolant valve, exhaust muffler assembly center, clamp assembly exhaust pipe, two gasket exhaust pipes, and added coolant. The contact related the failure to Technical Service Bulletin: 23-EM-009H (EHRS Coolant Leak Repair); however, the vehicle was not covered under the TSB. The manufacturer was made aware of the failure, and a case was filed. The failure mileage was approximately 18,500.

This is an extremely common issue plaguing Hyundai & Kia vehicles with the Theta III 2.5L Turbo engine, Such as Kia K5 GT, Hyundai Sante Fe, Hyundai Santa Cruz, & Hyundai Sonata N-Line. Its a failing ITM (integrated thermal management) unit or otherwise known as an ITMS unit. There is a rod within the ITM that prevents proper control of the flow of cooling the oil and engine coolant of the engine. Results in Cooling issues, such as a cold lower radiator hose while the engine is hot, or 'limp mode' during acceleration, that causes a sudden loss of power while trying to merge on the expressway. There has been other Kia models and years that have had TSB's related to fixing this issue, but Hyundai has released nothing. I have uploaded an example of one of the TSB's that do not apply to my car. Technical symptoms often include: Fans running 100% full duty (high) while the lower radiator hose stays cool. Or Fuel dilution or a 'rich' running engine. Because the engine is overcooling that keeps the car's fueling rich and in a open loop mode affecting emissions and contaminating oil. Personal Details of exactly what happened when i noticed mine was failing. I ran home on my lunch break, and while accelerating on a ramp to get up on a highway, my car started beeping and flashing "Engine Overheated" and i immediately let off the gas with preparation to pull over. The second i left off the gas, the coolant temp within 1-2 seconds went from a little over 3/4 the way up the gauge back to normal a little below half temp. I resumed driving a 3 mile drive back to work, with it showing normal temps the rest of the way. I popped the hood when i got to work to see if coolant was low, and it was completely normal, a little over halfway between the min/max lines. The car continues to run hot, often with the cooling fans running at 100%.

See attached document for complaint.

Reported this previously, but more information was gathered, thanks to collision mechanic who guessed immediately when he heard 2023 hybrid Sonata - he said "they're notorious for it." Was at a stand still in a parking space/lot I know well. Cautious driver, watch my speed, very aware of other drivers, quick reaction time. Incident mid day, no pedestrians, distractions, no moving traffic. Vehicle doors shut, seat belt on. Not on incline. Pulled into parking spot I use weekly, spot has parking curb. Was at a full stop. Realized I had not pulled into the spot quite far enough, and attempted to inch vehicle forward. (Do not recall any warning lights, but this car usually alerts at literally anything - even shadows.) Very lightly applied gas to inch forward, slowly. Felt slight "scrape" of undercarriage on the parking curb. Put car in reverse, lightly applied gas to inch back. Car did not rev, no screeching tires, it was at a standstill previously. Was in Eco mode. All seemed normal, until vehicle suddenly launched UP the parking curb, full force, and into a building pillar directly ahead. The car never moves with that much force, I'm not a pedal-to-the metal driver. Eco mode on. No airbag deployment, injuries, etc. Sheriff took report for the building, simple incident. I couldn't make sense of it. I know how overly cautious I am while parking, what I do, and don't do. Took responsibility, but was still analyzing a week later, and explained what I remembered to the mechanic. He guessed right away. Said Sonatas were notorious for it. He said they're known for randomly applying the ebrake unexpectedly - and also randomly releasing the ebrake - and aggressively (and silently) switching from electric to gas when met with resistance, aka the parking curb. Insurance totalled the car. 2.5 years old, 17k miles. This was my 3rd Hyundai in 20 years, others were great. Discovered 40,000 Elantra hybrids, same year as my Sonata, were recalled due to "unintended acceleration."