The contact owned a 2015 Hyundai Sonata. The contact stated that while driving at approximately 60 mph, the vehicle decelerated independently while the check engine warning light illuminated. The vehicle was taken to an independent mechanic where it was diagnosed that the sparks plug and the PCV valve needed to be replaced. The vehicle was repaired however, the vehicle check engine light recurred. The vehicle was taken to the dealer where it was diagnosed but the failure was undetermined. The vehicle was taken to another dealer St. Charles Hyundai where it was diagnosed but the check engine light continuously illuminated. In addition, the contact mentioned while driving, there was a pop noise and noticed white smoke was coming from underneath the vehicle. The contact pulled over to the side and exit the vehicle. The fire department extinguished the fire. A police report was filed. The vehicle was towed to the tow lot and was destroyed. The dealer was not contacted. The manufacturer was not notified of the failure. The approximate failure mileage was 143,000.