When the diagnostic code P0440 OBD2 is set, it indicates that there is a fault in the EVAP (The evaporative emission control system) system, i.e. one of its components is not working properly. Parts of the Evaporative Emission Control System (EVAP) include the gas blanket, fuel lines, purge valve, carbon filter, and other hoses.
The function of the EVAP system is to prevent the escape of fuel vapors from the vehicle’s fuel system. The fuel vapors are routed through hoses to an activated carbon filter, which stores them so that when the engine is running, a purge control valve opens, allowing an intake vacuum and diverting the fuel vapors into the engine.