2017 Altima check engine reset

Hello, P0456 represents an evaporative emissions system concern - specifically the detection of a very small leak of evaporative gases from the system. As long as you have made sure the fuel gap is not the source of the issue, the next step is to use a special piece of equipment that will fill your system with smoke vapor. The reason this is done is because the leak will show up where the vapor escapes from. This is a definitive way to find the leak. There is no way to guess at ay specific location to check first, and no way to verify the source of a leak unless you have something that make the leak visible - as with smoke vapor. Have you cleared the light after checking the fuel cap? The light will not quickly go off by itself, and the code you have is a "memory" code, not an active one. A diagnostic tool should be used to clear the code so you can drive and see if the problem comes back. It may not. If it does, the testing I've suggested is the next step. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops