The contact owns a 2015 Kia Forte. The contact stated that the vehicle had been taken to a local dealer and was diagnosed and determined that the catalytic converter and spark plugs were faulty and needed to be replaced. The contact stated that the parts were replaced; however, soon after the repairs, while her husband was driving 40 MPH, the transmission started slipping and failed to shift properly. There were no warning lights illuminated. The contacts husband was able to drive the vehicle to the residence and then the vehicle was towed to the same dealer for a second diagnostic test. The contact was informed that the engine needed to be replaced. The vehicle was not repaired. The manufacturer was not notified of the failure. The approximate failure mileage was 137,000.