mustaphababakalli ,there are literally 100's of reasons why this light is on. the best thing to do would be to place your car on an analyzer to find out which code it displays. Places like Autozone etc. will do a check for free. Start with that.

There is something wrong with your car. It could be anywhere from the intake to the exhaust, and the only way to tell is to plug in an OBD-II scanner to read and clear the code. As oldturkey has said, many national shops offer a code reading service for free, but you may want to trust your local repair shop to the actual repairs.

We used to get this error about 3 times a year. A $10 replacement gas filler cap solved our problem for a few years now!