Toyota Purge Solenoid - 90910-12274

A "rusty mess back there" might offer several possible sites for a leak. It might be worth doing a bit of diagnostic work to find where the leak really is.

 

I do this in my sienna van when the check engine light comes on I don't even need to check the code usually predominantly in the van apparently this is the main thing that the light lights up about and I've done it twice You can try it on the Prius but when I'm in the back of the van I also look around the charcoal canister I look for other possible areas of leak and distress so far haven't found any I have been away from New England for 25 years so it's been a while since I've dealt with that rust and corrosion thank goodness but give it a whirl while you're back there Do you smell fuel see anything wet that's not snowing ice etc use good judgment and common sense.

 

But put yourself in the position of regular members who spend time helping members with questions.

Someone comes along and asks something like "P0446 is present and returns quickly. Has anyone had any luck with just replacing the purge valve".

The full correct answer to the question asked is going to be, everyone whose leak actually was the purge valve will have had luck with just replacing the purge valve, and everyone whose leak actually was somewhere else, and who tried just replacing the purge valve, will not have had luck, and will still have a leak.

So if the first yes-or-no reply you get comes from someone whose leak was the purge valve, it'll be yes, and if it's from someone whose leak wasn't the purge valve, it'll be no. Both answers are perfectly correct, depending on where their leak was, and both answers are either helpful or unhelpful to you, depending on where your leak is.

So there's a good chance you'll eventually end up at the question "ok, I'm tired of this, how do I solve the problem?", and sometimes we end up skipping ahead and answering that one early.

Edit: that being said, because P0446 refers to an expected pressure change not being seen when the valve is actuated, a problem with the valve itself certainly is worth checking for (and the troubleshooting steps have you do that, at step 3). Then if the check shows the valve isn't working, you'll know 'yes' is the answer to your original question.