Large Leak Test
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
This tests for large leaks and blockages in the EVAP system. The PCM will command the EVAP vent valve ON, closed and the purge valve and the vacuum pressure switching solenoid ON, open with the engine running. This allows engine vacuum into the EVAP system. The PCM then commands the purge valve OFF, closed sealing the system. The PCM then monitors the Fuel Tank Pressure (FTP) sensor signal in order to determine if there is vacuum decay. A rise or rapid increase in pressure indicates there is a large leak in the evaporative emission system. If the PCM detects the vacuum level was not achieved and vacuum decay was evident for two consecutive trips, the Malfunction Indicator Lamp (MIL) will illuminate, and DTC P0440 will set.