P0446/P0440/P0441

good post!

This isn't exactly true.

A P0440, 441 & 446 could also be set from a loose gas cap or cracked/damaged line. It's does NOT necessarily mean that the EVAP canister is defective.

I've had MANY customers have these codes due to gas caps being loose or aftermarket with the valving be different.

The first things I would do is:
1) check gas cap for security. If it's loose, then there ya go.
2) if cap is tight, remove cap and check gasket and filler neck for any dings (from gas pump nozzle)
3) check all EVAP lines and make sure that they're on the airbox, CCV VSV, Purge VSV, etc.
4) check EVAP canister for damage/cracks (visual only unless you have a EVAP pressure tester and/or smoke machine)
5) take it to Toyota if these terms are beyond you and ask that a Master Technicain could work on it rather than the Express lube or rookie kids...

Good luck!

Sorry to have to pipe up again, but that's incorrect. I can think of no scenario where P0446(evap vent control solenoid CIRCUIT FAILURE) could be set by a gas cap OR a cracked hose. The code itself narrows it down to the control primary, NOT a pressure problem, purge problem or otherwise. That doesn't rule out a mis installed connector, or a gas cap loose for P0441, P0440. But Ive heard your argument from others before and my opinion is that they claim to have fixed P0440,1, and 6 before completing the EVAP drive cycle, the customer takes the car, and they celebrate a job well done, but two days later the car comes back and they forget to tell inform the rest of us that "nope, it wasn't the gas cap afterall".
If you could think of a possibility where a leak could cause a circuit failure, i'd like to hear it.

exactly right!

I think we can all agree that for these EVAP problems, one cannot assume the problem is completely fixed until the vehicle has been out on the road for enough time (several days) to verify that the problem has been resolved. I have to sympathize with the professionals who have to deliver the vehicle back to the customer with a higher degree of confidence than that. However, when we first consider our options, we should look at the most likely culprit for the vehicle involved, based on other users' experience and published data; in the case of the '01 Corolla VSV is listed as a common problem for these codes, so it's logical to go there first. If it turns out that's not the problem, then a full diagnostic approach would of course be warranted. In my case it was the VSV (CEL did not come back after I replaced the VSV), as the odds might have predicted.

Pattern failures are great for instances just like this! But unfortunately or fortunately as a dealer tech my scan tool has the ability to run the forced monitor on the evap system before the vehicle is returned to the customer to verify whether the repair was successful or not. There are some instances in regards to fuel tank level etc where the results of the forced monitor are inaccurate versus the real drive cycle but I unfortunately don't have the luxury of trying parts and clearring the dtcs when I think it's repairred and having the customer drive it till it does or doesn't! My customers won't accept tht method most of the time! Sometimes with real intermittents it's unavoidable but for the most part with evap dtcs it doesn't have to be done this way! Assuming your competent enough with any scanner, a smoek machine and a dvom that is! Like I said pattern failures are an awesome resource and I use them daily but it's not the only way! I've lost count of how many times I've seen new gas caps on leaking systems!

actually, you're right on the gas cap not setting a P0446. But you can get a P0446 Evap Emission Control Vent Control Malfunction due to broken, damaged, missing or defective lines off the EVAP canister.
A 446 is not necessarily a "vent control solenoid CIRCUIT FAILURE". It's a vent failure. Could be from a solenoid, could be from hoses or piping being bad, purge line, or solenoids. Not JUST solenoids. Anyway, my bad. Sorry about that.

To Corrola: I wasn't discussing the proper approach, or where to start a diagnosis. I agree that a tech willuse his past experience and previous knowlege to decide where to start for the fastest and most accurate diagnosis and that not all techs will approach every problem the same. I was informing that the P0446 setting parameters do not require a leak or blockage in order to set. Rather an open, short or incorrect voltage in the control circuit of the vent solenoid would be the correct setting conditions.

To 87AE86: If my code definition is wrong, then I would be wrong as well. Accordingly, your definition " Evap Emission Control Vent Control Malfunction" sounds very similar to mine "Vent solenoid circuit failure". I would guess that to accurately discover which definition is right would take more than a phone call to the software designers, but as per the conversation with Corrola, in this tech's experience(which has served me well), a leak, blockage, or otherwise wouldn't set P0446.

But this all hangs on the proper setting parameters of P0446. If it wasn't a "vent control circuit malfunction" and instead was a "vent solenoid malfunction" then I would have to amend my statement and consider your argument.

I am working on a 1998 corolla that is showing p0446 an p0441 but not p0440.

I noticed two things that I am not sure will help the poster as far as symptoms go, but:

1. When filling the gas tank with the engine on the rpm's drop and fluxuate until the throttle is blipped.

2. When removing the gas cap and listening, there is a glug glug sound. The same sound that happens when one pours a liquid through a small opening and air is sucked in.

Not sure if the adds anything but hope it does.

Thanks for the post and welcome to the forums!

Are those supposed to be tips that the valve or solenoid is bad on those cars!

I am not sure as I am a DIY newbie. I have just started to do my research on what this could be and stumbled on this wonderful thread.

This is awesome, my gf's 98 corolla has the same issue as everyone has been talking about here, codes 0440,1, and 6. Reading this has been very helpful. I am about to buy the car from here but this cel has been worrying me as the car will have to go through emissions before it can be registered. I haven't begun to try and fix the problem, just doing my homework first. Has anyone tried to have the dealer replace the entire canister as per the other persons post about the extended warranty on the evap system?

Does anyone know where to get a VSV for a 1999 Prizm/Corolla?

I think you'll have to go to a local Toyota dealer, which is what I did. They had it in stock. The on-line parts suppliers don't seem to carry this item, as far as I can determine. Anyway, the part number for this item on my 2001 Corolla was TO90080-91233. I am located in Canada, I don't know if this number would be the same at a US dealer, but my guess is that it would be the same.