Check Engine Light On problems of the 2005 Kia Motor Optima

: the contact stated without incident the check engine light illuminated. The dealership determined the fuel cap was not properly tightened, then checked for diagnostic codes. There were no codes found and the light was turned off. Fifteen minutes after the vehicle was taken from the lot, the light illuminated again. The vehicle was taken back to the dealership who expressed the fuel cap was not tight enough and there were still no codes. The light was turned off. The light illuminated a third time; although the vehicle was not refueled.