Canister Purge Control Valve: Description and Operation

Evaporative Emission System (EVAP) Valve







The evaporative emission system (EVAP) valve is used to open and close the connection between the EVAP canister and the intake manifold. The valve controls the flow of hydro-carbons (fuel vapor) from the EVAP canister to the engine intake manifold using the vacuum in the intake manifold. This ensures that hydro-carbons stored in the EVAP canister are used in the engine combustion process.

The valve is an electro-magnetic valve which is powered from the system relay. The evaporative emission system (EVAP) valve is closed when in the standby position (open-circuit).

When the engine control module (ECM) requests that the EVAP canister should be emptied (the hydrocarbons stored in the canister should be released into the engine), the engine control module (ECM) deploys the evaporative emission system (EVAP) valve by grounding it using a PWM signal. The engine control module (ECM) is able to govern the extent to which the evaporative emission system (EVAP) valve opens and adapt the emptying of the EVAP canister based on how full it is, engine speed, load etc.

The engine control module (ECM) can diagnose the evaporative emission system (EVAP) valve. The valve can be activated using VADIS/VIDA.

The evaporative emission system (EVAP) valve is close to the intake manifold.