DTC P0446: EVAP Vent System Blocked Or Restricted: Description
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
This DTC tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid open and the EVAP canister vent solenoid closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid closed and the EVAP canister vent solenoid open. The control module monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near zero inches H2O in a calibrated time, this DTC sets.