I had this same thing happen on my 2006 LX470. My dealer, Performance Lexus in Cincinnati, told me the error code showed a gas cap problem. Upon investigation they found that the gas cap was on tight but the "boot" around the gas filler had gotten loose and they tightened it so that it sealed properly. It fixed the problem. Fortunately for me my car is a certified used vehicle and still covered by warranty. Good luck!