On the 2002 Chevy Prism, the P0446 is pointing to a problem in the EVAP Vent System. If DTC P0446 is the only EVAP DTC set, the most likely cause is an inoperable EVAP pressure switching solenoid. This Solenoid is mounted to the EVAP Canister, located under the vehicle, towards the rear. Carefully inspect the rubber vapor hoses to/from the Solenoid for any cracks, holes or loose/missing connections. Inspect the electrical connector and wire harness for any loose, broken or damaged wires. Inspect the Canister for any dents, cracks or holes. If the visual inspection checks ok, replace the Pressure Switching Solenoid.
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