Date registered: Oct 2003
Vehicle: 500SE AMG, E350 4matic, GL 450
Mentioned: 0 Post(s)
Quoted: 80 Post(s)
If I remember correctly, the "gas cap code" is PO400 or P0442 (or something like that). It not only could be the gas cap. It could be a small leak in the fuel system. As suggested, get a new cap, reset the code at Advance Auto. If it comes back again, go to an good independent that has the machine that can find the leak. It is some kind of smoke machine. I had it done on my old w163.