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Been dealing with trying to figure out the cause of codes 0446 and 0441 on my 2000 Limited for a month or so. Found lots of good information in this and other threads, http://www.tundrasolutions.com/forums/1gen-tundra/101872-p0446-problem/ but haven't been able to track down the problem yet.


A few months ago I notice a drop in gas mileage, down to 12.5 mpg from my normal 14.5 mpg. it was time for new plugs so I replaced them with the OEM Denso along with the air filter and PCV valve. Didn't see any increase in mileage and the truck is running fine so I just chalked it up to winter gas. A few days after doing this the check engine light came on with codes P0446 and P0441. I have check all the hoses in the engine compartment for blockage and cracks and found a couple that seemed like they might be a little loose so I replaced them. Checked the VSV valves with the battery test to see if they were working. The one mounted on the engine didn't seem to be working properly so I replaced it. Still getting codes. Pulled the Evap canister to check for cracks or anything rattling around in it while I shook it. Appeared to be fine so I reinstalled it and checked all the hoses again. Checked the hoses leading back to the fuel tank for obvious signs of cracks or being loose. Installed a new factory gas cap and the filler neck looked to be fine. Still have pressure release when the cap is removed. Haven't been able to check the hose connections at the fuel tank yet. I don't smell gas anywhere so I don't suspect a fuel leak. Rechecked all the vacuum hoses in the engine compartment to make sure I hadn't knocked anything off. Installed another new PCV valve just to be sure it wasn't that. Inspected all the electrical connections associated with the Evap system and didn't see any sign of broken wires or bad connections. Not sure if this is a related problem but a few weeks ago it occasionally started to stumble a little when I would go to start it. Turn the key it fires, stumbles and dies the starts right up the next time. Yesterday when I came out after work it did this a few times and acted like it didn't want to start. Had to try to start it a few time and it sputtered. When it finally started it ran fine. Checked the codes again to see if there were any new ones but still just the 0446 and 0441. Anyone have a good idea on what else to check at this point? Thanks for any help offered.
 

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I've had the same Evap codes haunting me for too long now but I've finally won. I have an 03 tundra v8 that sets a P0442 & P0446 code every spring. There is a toyota service bulletin for P0446 that says to test and replace the VSV valve (also more commonly known as a purge valve) in the engine compartment. Didn't work. There is also a service bulletin for P0442 that says to replace the fuel filler neck. Did that…..didn't work. Replaced the fuel cap…..didn't work. Tested the evap canister shut valve and found it to be bad. Replaced it and it still didn't work. Finally I realized that the evap canister must be saturated with fuel, which caused the shut valve to go bad. Removed the canister assembly and inspected it for any signs of cracks, damage, or spider webs. Finally purchased the very expensive evap canister assembly (with another shut valve included) and installed it. Problem is fixed. No more dtc, evap monitor is now complete.
 

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Thanks for the response. I am pretty sure my vapor canister is bad too. I have ordered one and it should be here tomorrow.
 

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Hmm, I am chasing a PO446 error code and being told a swan song by my local dealership. They want $800 to replace the solenoid value at the canister and the three short hoses. Sounds pretty expensive to me. Watched a YT video of someone with a 2003 with the same problem and his dealership told him the canister was cracked, but it wasn't. They wanted a $1200 repair for the canister, but he admitted he was discounted to $700. He fiddled a bit, can seemed fine (his is by the gas tank, but mine is under the hood). He pulled the solenoid valve from the can and tested it, not working.

So, he then went and price checked some Toyo dealerships and got offers from $50's-67. Bought and installed it and voila. Noting what I was just quoted and the experience noted in the video, I have to say I am shying away from the dealership.

Jdaniels, what part did you use and which supplier (which dealership parts department or 3rd party?) did you source from, because I'm hearing stories the can can cost >$500 alone. For my 14 year old truck (2001 Toyota Tundra SR5 Access Cab 4.7L 2WD) I do not care to just throw money away needlessly.
 

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Hmm, I am chasing a PO446 error code and being told a swan song by my local dealership......
On your truck P0446 is most likely to be a failed vacuum switching valve on your charcoal canister. The part number for your charcoal canister is 77740-34080. I believe Toyota does in fact sell your VSV separately from the charcoal canister, it's part number 90910-12130. Over $100 at the dealer, about $50.00 on eBay.

It's the silver and blue thing.

If you're willing to make the effort you can fix the VSV for zero cost. Remove it from the canister, take it apart by squeezing the four sets of little ears together and you will find either the piston is stuck or the o-ring seal has failed.

VSV Repair.jpg

 

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Discussion Starter #7
I bought an OEM Toyota Denso canister part number 77740-34080. I shopped around online and got it with free shipping. I can't remember where I got it but if you google "77740-34080" you will find many places where it is available for under $300.
 

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I've been looking around and found one site (TPD). They have the canister for a hair under $300, but no picture and it wasn't clear if the VSV was included (see pic mibro posted). The VSV can also be bought from them for about $116 without the actual canister.
 

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Did anyone notice a strong oder when idling with this problem?

I noticed an oder one day and later the check engine light came on with these codes.

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I have the P0446 code. Lots of cracked hoses. Looking for a parts diagram for the EVAP sytem (hoses also) for my 02 tundra limited 4.7L. TIA.

Nevermind. Got what I needed. Thanks for the information in this thread.

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