Posted 08 October 2008 - 10:14 AM
Hmm, what I can tell you is that the P0446 code is an EVAP code, directly meaning "Evaporative Emission Control System Vent Control Circuit", and on the RX330 it's usually directly tied to the charcoal canister. I don't know about a catalytic converter being the issue. That usually results in air/fuel/exhaust codes... not emmissions.
Some people have said/thought a loose gas cap can trigger this code, but other say no way. On the RX300, the P0446 code is often a 'phantom code', meaning it shows up even when nothing is really wrong... then goes away (I've had that on my '99). One thing for sure, a new charcoal canister always fixes the problem. I don't know if that scenario directly equates to the ES300, but they sure share a lot of the same DNA.