EVAP Purge Valve Operation
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.
If the EVAP purge valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The PCM tests for this by commanding the vent valve closed and the pressure switching valve open causing a vacuum, in the entire EVAP system. PCM continues to operate the purge valve until the vacuum is lowered to a specific point, at which time the purge valve is commanded closed. PCM monitors the fuel tank pressure (FTP) sensor. If the PCM does not detect a drop in vacuum, or the vacuum increased beyond the specified limit, for 2 consecutive trips, the MIL will illuminate, and DTC P0441 will set.