It can be costly to fix problems on cars. But the Check engine light comes on when one of the sensors is seeing that some condition is out of range. At that could be something as simple as the sensor being bad, or a loose gas cap, or maybe some component has failed. The only way to tell is to get the stored code. While a dealer or auto repair shop will charge for it, many auto parts stores will retrieve it for free. Get the code and post it back here.