Error code P0446 - and i've tested a lot of stuff
 

So wifey inherited this car and a error code is preventing it passing its emissions test which means she can't get it registered.

The Error code is P0446 with the message "Evaporative Emission System Vent Control Circuit".

I tested the purge and vent solenoid and they both seem fine. When i blew harder into the vent solenoid, applied power so that it closed the valve and then removed the power it stayed stuck in the closed position, but i purchased a new unit and it did the same thing so i'm guessing its supposed to act like that. If i don't blow hard, it opens and closes just fine.

Gas cap has also been replaced.

Other info that may be relevant is that i was originally keeping the gas level between half and 3/4 tanks gas as i had reset the code after replacing the gas cap and had to take it through drive cycles and this was recommended. I had no issue when i was putting gas in. But when the check engine light came back on, i didn't worry about maintaining that gas level and when it got low i went to refill it and the handle kept triggering like it was full but the tank was only 1/2 full.

I thought that because of the gas filling issue that there might be a blockage. I removed the gas cap and blew into the hose that connected to the vent solenoid and was able to blow in it several times without issue.

And i'm not sure if its related, but when i run a I/M readiness scan, i was never able to get the CAT or EVAP to go green, and i had a Pd DTC 1 code.

There was no other codes on the scan, although it did just trigger the P0449 which i believe is because i had previously disconnected the vent solenoid.

I'm guessing at this stage it time to take it to a mechanic who has the tools and equipment to run a more thorough diagnostics. But i thought i would check here in case someone had an idea. I think i saw someone else had this problem and ended up having the PCM reprogrammed or something like that.

I've had this code and its sister codes for three years now. I've replaced EVERYTHING related to this code at this point. About a month ago I ran Lucas Oil Deep Clean and I don't know if it is just a coincidence but I haven't had it on since.

Thanks for the tip. I've gone ahead and added that to the tank.

How long did it take before the code dropped after added that?

About four or five days of driving for me.

Evap vent solenoid
 

Go to the left rear wheel and look up under the fender. You will a black solenoid attache to a metal bracket. This solenoid vents fuel vapor back to the engine to be burned. When they fail, they give an evap code and the gas nozzles at gas stations click off before full. Happened to my 2000 SS.