Enhanced Evaporative Emission (EVAP) Control System

The [1][2]EVAP control system prevents the emission of the fuel vapors.

The fuel vapor generated in the fuel tank while driving or idling, passes through a tank pressure control valve and enters the EVAP canister where a charcoal element absorbs and stores the fuel vapor. The enhanced EVAP canister is purged, or cleaned, in the same way as a non-enhanced EVAP canister. The tank pressure control valve operates as follows:
^ When the [1][2]EVAP tank pressure control valve closes under the following conditions, the vapor passage of the tank pressure control valve also closes.
^ The engine is OFF.
^ The engine is running, the vehicle is stopped and the fuel level is higher than the specified value.

Therefore, when the pressure of the fuel vapor generated in the fuel tank becomes more than the specified pressure, the tank pressure control valve opens and the fuel vapors enter the EVAP canister.

However, when the engine is running and the fuel level is lower or higher than the specified value, the [1][2]EVAP tank pressure control valve is turned ON by the PCM and the vacuum is applied to the diaphragm of the tank pressure control valve. With vacuum applied to the diaphragm, the tank pressure control valve opens, equalizing the pressure between the fuel tank and the EVAP canister.

The EVAP canister vent valve and the fuel tank pressure sensor are provided so that the PCM can diagnose fuel vapor leakage from the [1][2]EVAP control system. The EVAP canister vent valve is usually open but is closed by the PCM when checking for any leakage.