DTC P0446: EVAP Vent Valve Performance: Description

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

This DTC tests the Evaporative (EVAP) emission system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid ON and the EVAP canister vent solenoid ON. 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 OFF and the EVAP canister vent solenoid OFF. The control module monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

For the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves, see EVAP VALVE LOGIC table under DTC P0440: EVAP SYSTEM - LARGE LEAK.