When the engine is on, the Evaporative Emissions Control (EVAP) system's job includes taking in fuel vapors and then letting them go into the intake manifold. Some of its components are fuel tank filler neck cap, fuel cut valve, EVAP canister, drain filter, drain valve, fuel tank pressure sensor, pressure control solenoid valve, shut-off valve, vent valve and purge control solenoid valve. This system works by controlling the fuel tank pressure and retaining vapors in the charcoal canister until they are absorbed by the engine during purging. The EVAP system contains a number of valves that prevent fuel from getting into it when refueling is done. A relief valve within the cap of the filler neck equalizes pressure inside the tank during loading operations. Replacing component parts involves disconnecting battery negative terminal; unplugging electrical connectors; indicating and disconnecting EVAP hoses; removing mounting bolts or nuts before reinstalling items backward. That specific guidance is provided for each model or year.