First, as a "newbie" to the forum, I'd like to thank everyone who has already posted in other threads and offered solutions to this annoying and fairly prevalent (or so it seems) issue with the CEL, VSC Trac lights on and PO446, PO440 codes. I've tried many, but to no avail, unfortunately.

In summary,

• smoke tested the system, no leaks (yay!)
• replaced the upstream (before the converter) 02 sensor, reset codes = worked briefly, then lights back on.
• replaced the VSV valve/solenoid mounted above the vapor (charcoal) canister, reset the codes = worked...for a while, then lights back on. (Though after doing this, the lights remained off for the longest time following an attempted fix and allowed me to at least get it inspected, passing.)
• have not replaced the OEM gas cap, but after reading many posts on this topic, it's seems this rarely is the fix
• I'm now considering replacing the vapor (charcoal) canister in the back, but really don't want to if it's not necessary.

And, for what it's worth, I do periodically smell gasoline as driving along. Not too often, but once in a while.

Short of taking it to the "stealership" and paying a $95 diagnostic fee to tell me the same codes and shrugging shoulders, anyone have any other suggestions? Some threads suggested getting a canister from a junk yard which would be cheaper, and I'm all in favor of in certain circumstances but with the canister wouldn't you rather have a new one than used, which has so many unknown variables? I've found a new one for about $325 but, again, don't wanna spend it if it ain't gonna solve the problem.

Finally, I'm not going to just ignore the lights either. Need the skid/traction control working for the upcoming winter when the wife drives it.

Thanks for ANY other solutions offered!

Get yourself an obd scanner so that you dont have to take it to someone just to scan it. 0446 is the valve or the wiring- being that you've changed the valve go back and check for a short in the wiring somewhere. As for the other code- swap out the other 02 sensor, check the solenoid, then the canister. Everything you'll read on it says change the gas cap too but I honestly cant believe it would be just the cap. If you can find a canister at a yard cheap go for it- if that fixes it, when it does it again go ahead and spring for a new one.

Subscribed....I periodically am getting P0440, P0441 and P0446, but not the VSC/TRAC lights. What's helped me the most so far (and kept it from kicking the CEL on every 250 miles) has been to NOT top it off anymore when fueling. Once the pump stops, that's it. I was able to go almost 2000 miles with no CEL last time so that's pointing me at the charcoal canister on my '01. I did throw a new factory gas cap at it, just to see if that helped, but I doubt it did anything.

Hopefully there's more insight to be learned....I still have a few months till it's time to get it renewed.

On a side note, when I get these codes, my VCS TRAC lights never come on. I checked when starting today as well, and they don't even turn on either. Any ideas why they wouldn't even light up when starting?

I'm in on the 440, 441, and 446 codes myself. Have been clearing the light periodically and ignoring, but need a proper solution.

Same issue here I guess I need to change out my VSV solenoid and see if that helps but I believe my charcoal canister is done for. I dont feel like spending the money to get a new one. WORDMAN there is one more VSV switch under the hood by the master cylinder try to replace that one as well.

Good ol' P0446

That's a great thread.

A $50 scanner was great for keeping track of codes and deleting them, and beat disconnecting the battery every 3-4 days.

My fix ended up being a new filler pipe and a new gas cap, and I was ready to spring for a canister. Glad I saved some $$$. If you have rust, seriously consider the filler pipe because it's in a bad location for gathering salt spray and not getting rinsed well from car washes.

You can also easily test all 3 valves with a 12v battery. connect batt (polarity does not matter) and trigger the valve while blowing in tubes. I have 440 and 446 but also have CAT "incomplete" and am currently troubleshooting.
C

Keeping this post alive...where do I hookup the 12v battery to the valves in order to test them? Is there a write-up on this?

I have the P0440 & P0446 codes. The CEL light wasn't on when I purchased it but it has come on several times since (about 300 miles driven) with these codes. I purchased the truck about 2 months ago and it has 237k miles.

Maintenance I've done since owning:

• Replace the non-OEM gas cap with an OEM.
• Remove and clean the Throttle Body and MAF
• Change air filter, oil, oil filter, PS (ATF) flush and brake fluid flush.
• Replace PCV Valve and grommet
• Stopped pumping gas after the first click of gas pump shutting off
• Put STP fuel injector cleaner in the gas tank (I drove until the gas light came on and have filled up once since then. I was getting these codes prior to using the fuel injector cleaner).

I'll take it to an emissions testing place this week to test for line leaks. I know the truck was initially purchased in the DFW area and has been here in Austin for about the last 5 years. There's no under-carriage rust, so doubt any rust on the fuel neck pipe. I believe the 02 sensors were replaced before I purchased it but not certain.

So my options are to check for vacuum leaks, test the valves and then charcoal canister? Any other thoughts or suggestions? I don't want to just keep ignoring these codes.

Remove the sensor- 2 contacts<->2 battery terminals. There really is not much more to it than that. I got Catalyst to become "ready" and pass smog but still throwing 440/446 even though the 3 valves tested ok. I am planning on dropping my canister and doing a "refurb" on it replacing the carbon granules etc. and doing a pictorial write up during the process. Not in a hurry though. There is a LOT of info re these codes- and many experiences and opinions. I just hope in my case it has nothing to do with the pressure sensor on top of the gas tank- that would suck. A proper battery of tests done at a shop could id that so might end up going that route.
Good luck.
Clifford

Anyone who is getting these emission system related codes really needs to seal their charcoal canister. The bottom of it can crack at the seam and will cause intermittent codes depending on how bad it is. Just bust out some jb weld and smear it all around the bottom seam of the canister. That is what I did after doing everything else. No codes in 10k miles (knock on wood). No need to buy a new one.

Please note that the gas caps are often not left tight enough to seal properly by station attendants .Topping off leads to overfilling which can drop gasoline into the vent hose leading to the canister which is designed to absorb hydrocarbon fumes only and will often times fail to vent after such topping off.Keep cash on hand to order gas by an amount you know will be enough without the gas being run to round off the dollar (and save on credit card charges).
I had a cap that fooled me for some time as the gasket (seal) inside of it was cracked 3 times on the side facing away and towards the cap top so check both sides of the gasket as cracks will spread open as the cap is closed tightly.
Finally,I have an 01 SR5 that seems to be showing emission faults other 3rd gen owners on the site have mentioned but it's been good so long otherwise.

Did smoke test on mine and found smoke coming out the top of filler tube. Ordered gas cap. If not that then the filler neck


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This was one of the codes that I️ chased down for a couple months.

First, bought a new OEM gas cap (cheapest and quickest fix). Well that didn’t work.

At every fill up, the pump would shut off every few dollars. Most frustrating thing ever haha.

Did some more research and figured it was either the charcoal canister went bad (usually go bad from people topping off during fill ups) or the overfill check valve on top of gas tank.

Ended up finding a used charcoal canister for $80 on here and that fixed the codes. New OEM canisters are like $400 and I️ was not about to pay that

I did a refurb on my canister in June of 2017 and was easy. Cut it open, checked filter, replaced granules, plastic welded shut with a soldering iron. Easy. Pictures suck but never seen anyone else post a refurb so here goes:
2001 4Runner canister refurb - Google Photos