Service Engine Soon Light w/ code P1456

Code P1456 means that the Evaporative System has detected a small leak. The Evaporative System captures and stores fuel vapors from your gas tank so that they do not leak in to the air. Here is a link that will explain it a bit. http://repairpal.com/evaporative-control-system This is best done by using a smoke machine to locate the leak. One cheap way to start is to get a genuine Infiniti gas cap from the dealer and replace your old one, sometimes the gas cap rubber seals get old and do not seal as well any more. If, after you replace the gas cap, the light does not go off in say a week to 10 days, while keeping your fuel tank between 1/3 and 2/3 full then you will have to have the more extensive diagnosis to locate the source of the leak.