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Circuit/System Description

WARNING: This page is about a different car, the 2009 GMC Envoy and 2009 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The engine control module (ECM) tests the evaporative emission (EVAP) system for a large leak or 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 to verify that the EVAP system is able to reach a predetermined vacuum level within a set amount of time.