P0025 Mercedes-Benz -

Question

I have a 2007 Mercedes ML350 with mileage around 65,000. For several weeks, the 'check engine' light would go on and then a couple of days later it would go off. Thinking it could be the gas cap, I bought a new one from Mercedes . . . it went off. But soon after, I got the same intermittant 'check engine' light. Then I found that when I filled the gas tank, within a day or so, the 'check engine' light went out. But when the tank was down 1/4 (i.e., 3/4 full), the 'check engine' light went back on. I've duplicated this at least half a dozen times. Yet, when I went to Auto Zone to have them determine the fault code, it was P0025, which relates to the cam shaft position bank two, over advanced. Any thoughts?