Purge Valve Leak Test

If the EVAP purge valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge valve OFF, closed; and vent valve ON, closed; sealing the system, and monitoring the FTP for an increase in vacuum. If the control module detects that EVAP system vacuum increases above a calibrated value, DTC P0496 sets.