EVAP Vent Restriction Test

A restricted or blocked EVAP vent path is detected by the PCM commanding the purge valve ON (open) and the vent valve ON (closed) allowing a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reach' d, the PCM commands the purge valve OFF (closed) and the vent valve OFF (open) while monitoring the FTP sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, DTC P0446 will set.