DTC P0446: EVAP Control System Vent Control Malfunction: Condition

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when excessive fuel tank pressure or a vent control malfunction in evaporative emission control system is present. Possible causes are:

Fuel Tank Pressure (FTP) sensor malfunction.
Fuel vapor hose blockage.
Open in wire harness.
Canister vent restriction.
Damaged canister vent side filter.
Canister Drain Cut Valve (CDCV) malfunction.
PCM malfunction.