The fuel evaporative emissions control system absorbs fuel vapors and releases them into the engine intake during operation, where they mix with the incoming air-fuel mixture. Each system uses a canister filled with activated charcoal to absorb these vapors, though the methods of control can vary significantly. A fuel filler cap equipped with a two-way valve vents vapors to the atmosphere if the system fails, while another two-way valve on the fuel tank regulates vapor flow based on pressure changes. Fuel vapor travels through vent hoses to the charcoal canister, where it is stored until the engine reaches a preset temperature, at which point a purge cut-off solenoid valve closes, allowing intake manifold vacuum to draw vapors from the canister. Checking the system is typically beyond the average home mechanic's scope, but the EVAP system is covered by a federally mandated extended warranty. The most common issue is a disconnected or damaged hose, which should be checked against the vacuum hose routing diagram. The purge control solenoid allows vapor purging when the engine is warm and cuts off vacuum when cold; testing involves checking for vacuum presence at the hose end and ensuring the solenoid opens and closes correctly when battery voltage is applied. The two-way valve should stabilize at specific vacuum and pressure levels during testing, and if it does not, it should be replaced. To check for a canister vent shutoff valve, look for a two-wire connector on top of the canister, and if present, test its functionality by applying vacuum and checking for leaks after disconnecting the electrical connector.