DTC P0446: EVAP Vent System Performance: Description

This DTC tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path. The PCM 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 PCM commands the EVAP canister purge solenoid Closed and the EVAP canister vent solenoid Open. The PCM monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near zero in. H2O in a calibrated time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent valves. See EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP  table.