Fuel Tank Isolation Valve (FTIV): Notes
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The FTIV is a PCM controlled solenoid that isolates the fuel tank from the rest of the EVAP system. The FTIV is a normally closed valve blocking the flow of vapors from the fuel tank to the EVAP canister. This prevents the canister from becoming saturated causing hydrocarbons (HC) to be released into the atmosphere in a situation where the engine does not run during a drive cycle. The FTIV will automatically open to relieve excess vacuum if the fuel tank vacuum reaches a maximum mechanical relief threshold value.