Fuel Tank Isolation Valve: Notes

The fuel tank isolation valve is mounted behind the fuel tank, near the EVAP canister. The fuel tank isolation valve is a PCM controlled solenoid that isolates the fuel tank from the rest of the EVAP system. The fuel tank isolation valve is a normally closed valve blocking the flow of vapors from the fuel tank to the EVAP purge valve and 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 PCM opens the fuel tank isolation valve during refueling. The fuel tank isolation valve will automatically open to relieve excess pressure or vacuum if the fuel tank pressure or vacuum reaches a maximum calibrated value.