DTC P0440: EVAP System: Description

The Evaporative Emission (EVAP) system is used to store fuel vapors to reduce amount of unburned fuel from escaping into atmosphere. PCM monitors the EVAP system for circuit faults in the fuel tank pressure sensor, EVAP purge solenoid and EVAP vent solenoid circuits. PCM also monitors the EVAP system for small and large leaks. During this test, PCM monitors fuel tank pressure sensor for an atmospheric pressure reading when all DTC criteria has been met with engine running. PCM will then command the EVAP vent solenoid on (closed) and the EVAP purge solenoid on (open). PCM will allow pressure drop in fuel tank for a certain length of time after which it will turn off the EVAP purge solenoid. DTC will set when a certain vacuum in fuel tank could not be achieved due to a large leak.