DTC P0446: EVAP Vent System Performance: Description

This DTC tests Evaporative (EVAP) emission system for a restricted or blocked EVAP vent path. Powertrain Control Module (PCM) commands EVAP canister purge valve on and EVAP canister vent valve on. This allows a vacuum to be applied to EVAP system. Once a calibrated vacuum level has been reached, PCM commands EVAP canister purge valve off and EVAP canister vent valve off. PCM monitors Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. DTC sets when vacuum does not decrease to about zero in. H2O in a calibrated time.