2006 Mercedes Benz ML350 Check Enging light on

I just purchased a 2006 Benz ML 350, with approximately 58,000 miles, this is the second day that I drove the car, and the Check Engine light is now on. I had not place new gas yet, but I did check and close the gas cap twice, the first time the engine light did went off, but this morning on my way to work thet check engine light is back on. I opened and close the gas cap again, but this time the light stay on.

There are no symptoms no shaking, only that the check engine light is constantly on. I sold my old benz ml450 for this reason. Should I be concern? Is this a serious problem or a known problem with the ML classes? Can the problem be permanently solved by replacing the gas cap?

Thank you very much