What is diagnosis code p0440 mean

This is an EVAP system trouble code. The EVAP system pulls gasoline fumes from the gas tank to the engine to be burned up instead of releasing them into the atmosphere. You could have a bad gas cap or a leak in the EVAP system. Make sure the gas cap is on securely. If it is, replace it, they're cheap. If the check engine light doesn't go out in a few days after replacing the gas cap you'll need to have the EVAP system smoke tested. Some leaks are so small you can't see them with the naked eye. Hope that helps! Jim