What's the 7e8 engine code Hyundai Sonata?

Unfortunately for You, the $7E8 and $7E9 engine codes mean bad news! No, just kidding -- they can mean literally anything. When the OBD-II tool that You're using can't read and translate the fault code data into hexadecimal format, it uses sort of "placeholder" codes. Your $7E8 code does indeed indicate that there's a fault with the Hyundai Sonata's engine, but without more information, there's no way to tell what that is. Your neXTStep should be to take the vehicle to a reputable auto parts store and see if they can scan it for You. It's usually free, so that beats buying a new scan tool. Perhaps if they can get more accurate error code information, we can further explore what's wrong with the vehicle.