DTC P0446: EVAP Vent Valve Performance: Description
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. 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 valve Open and the EVAP canister vent valve 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 valve Closed and the EVAP canister vent valve Open. The control module monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 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.
ON & OFF, OPEN & CLOSED STATES OF EVAP CANISTER VALVES
| Control Module Command | EVAP Canister Purge Valve | EVAP Canister Vent Valve |
|---|---|---|
| On | Open | Closed |
| Off | Close | Open |