0446 solved

I finally figured out the 0446 code on my 2000 Prizm. I went to the library and copied both the Prizm and Corolla service manuals. Switching between the two I was able to troubleshoot it down to the valve on the EVAP canister. A lovely place to work. Fun to get the canister down enough to remove the valve. I went to the Chevy dealer and it was hard and expensive to get the part from them. I went to the Toyota dealer and bought part number 90080-91233, valve, vacuum switching. Pricey at $75.00 but it did solve the problem. Now I have to work on code 0441, a small leak somewhere in the system. I hope this helps others with the same problem.

Thank You unknown2 Thank you!
I just got code P0446 and your post is very very helpful !!!!
This will save me much time in getting that little issue resolved. I have had my 1999 Prizm a week today and the darn light came on already. No real biggie though .. I like this sort of thing. I like being self sufficiant in repairing my cars. (It's a curse) (hah) DangerDude

I've had code 0446, and 0440 if I remember correctly, on my 02 Prizm. Its true that the code indicates that the evap valve isn't working, or at least isn't working fast enough. From what I found, one cause was over filling your gas tank. If you top off too much, liquid gas gets into the evap valve or canistrer and it can't work properly. For me, making sure not to top off has fixed the problem without needing to replace any parts. The check engine light did go back on once in a while until all the gas worked its way out. I think its been a good 4 months now since I've had that problem. I'd recommend something like scangauge (http://scangauge.com/) that lets you clear the codes and turn off the check engine light.

Thanks "mclapsad" I got the Helm manual for my 99 Prizm, what a great book! (expensive but excellent) Got my scan tool too. Cleared error codes and so far .. so good, no more engine light. I have no fear of the "check engine" light anymore! The Helm manual explains everything! I've been detailing the engine compartment now. Painting and polishing everything that's not spinning! I love the Prizm! DangerDude the happy mechanic!

I replaced the canister, replaced both vlaves - one by the canister and one by the engine, and replaced the gas cap. Service Engine Soon light with code P0446 remained on. I saved the fuel tank vapor pressure sensor for last as you need to drop the fuel tank to replace it. Replacing this one seems to solve the problem. Dropping the fuel tank wasn't as bad as expected. You can E-mail me if you want tips on this. Mine was tricky because I wanted to run the tank low and have run out of gas in the past due to a faulty gage. I share this because I hadn't heard anyone else having to replace the fuel vapor pressure sensor to solve this problem. I would still leave it at as a last resort.