Vapors are produced in the fuel tank due to external heat radiation or surplus fuel gaining heat before returning to the fuel tank. These vapors are captured and then purged by way of an activated charcoal filter. A purge valve is located between the intake manifold and charcoal canister, and is actuated to allow fresh air to be drawn in through the canister to purge the captured fuel vapors. A faulty canister purge valve will cause a check engine warning and is an emission relevant component.

Bosch Leak detection pumps ensure the evaporative emission system (EVAP) is functioning correctly. Leak detection pumps provide pressure so the system can be checked for leaks while other EVAP system valves are closed. A faulty leak detection pump will cause a check engine warning and is an emission relevant component.