Circuit/System Description

The engine control module (ECM) tests the evaporative emission (EVAP) system for a large leak or a restriction in the purge path. When the conditions for running are met, the ECM commands the EVAP canister purge solenoid valve OPEN and the EVAP vent solenoid valve CLOSED, allowing engine vacuum to enter the EVAP system. The ECM monitors the fuel tank pressure (FTP) sensor signal in order to determine the EVAP system is able to reach a predetermined vacuum level within a set amount of time. This turbocharged engine is equipped with a one-way flow check valve that prevents boost pressure from entering the purge line and EVAP system.