DTC P0440: EVAP System - Flow During Non-Purge: Description

The Evaporative Emission (EVAP) system is used to store fuel vapors as to reduce the amount of unburned fuel from escaping into the atmosphere. The EVAP system consists of the EVAP canister, Fuel Tank Pressure (FTP) sensor, EVAP lines and hoses, EVAP purge solenoid (normally closed), EVAP service port, EVAP vent solenoid (normally open) and fuel tank. The Engine Control Module (ECM) monitors the EVAP system for circuit faults in the EVAP purge solenoid, EVAP vent solenoid and FTP sensor circuits. The ECM also monitors the EVAP for leaks between EVAP vent and purge solenoid. When certain conditions have been met, the ECM will perform an EVAP diagnostic test at idle with no vehicle speed. DTC P0455 will set if a vacuum cannot be pulled on the EVAP system during the EVAP diagnostic system test indicating a large EVAP system leak or insufficient vacuum to EVAP purge solenoid.