The check engine light came on in the car. Upon having it checked at a local automotive shop, we discovered that the thermostat assembly is malfunctioning. This can cause the engine to overheat and shut off at any time which of course would be a severe danger. Additionally, a bad thermostat assembly in Kia vehicles can lead to engine overheating or overcooling, potentially causing engine damage and even a fire risk. Upon searching, this appears to be a common issue with the 2016 Kia Optima.