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Ok, thats good. Toyota did put out a computer update to take care of this problem to modify the values so this code isnt set when there isnt actually a problem. When the converter isnt the problem it is usually the oxygen sensor. As far as the P0446 that usually means the Evap canister has failed but could mean other things. Verify that the 3-way Vacuum Switching Valve (VSV) on the canister operates correctly. When the VSV is not grounded, the Fuel Tank Pressure (FTP) sensor should be connected to the canister side of the system only. When the VSV is grounded, the FTP sensor should monitor only the fuel tank. Monitor the FTP sensor, unplug the 3-way VSV, draw vacuum into the canister and verify that it will hold vacuum, and the FTP voltage will decrease. Test and verify that the purge solenoid and wire harness are all OK. The purge solenoid should apply vacuum to the charcoal canister when grounded. Also verify that the hose from the purge solenoid to the charcoal canister does not leak. Let me know if you have questions, thanks.
P0446 EVAP Vent Control Solenoid Circuit Malfunction - With Automatic Transmission
P0420 Catalyst Efficiency Below Normal (Bank 1) - With Automatic Transmission
The vapor pressure sensor is on the fuel pump and the VSV is located on the canister.
Here is a picture, let me know if you have more questions. Thanks