Good ol' P0446

[Terrapin]

So my CEL light came on a few weeks back. Had it checked at Autozone for free...P0446... EVAP. What I thought was most likely: charcoal canister, VSV, or best case a vacuum line. Brought it to the stealership this AM and none of the above. Just a loose gas cap according to them. An $80 + tax loose gas cap to be exact.

Has anyone had P0446 and had it be JUST the gas cap? I serously doubt that it the solution, but we will see...

At least they said no charge for Dx if the CEL pops back on again.

I'll report back if/WHEN the CEL lights up again

 

[techno]

I haven't had this issue, but I checked my fsm to see what it says.

These are the listed trouble areas

Vacuum hose cracks, holes blocked, damaged or disconnected
Open or short circuit in vapor pressure sensor circuit
Vapor pressure sensor
Open or short in VSV circuit for EVAP
VSV or EVAP
Open or short in VSV circuit for vapor pressure sensor
VSV for vapor pressure sensor
Charcoal canister cracks, holed or damaged
ECM

 

[01sr54x4]

My CEL is on as well... ran portable scanner, came up with same code. Did a lot of research online and it seems to usually be a PSV or Charcoal can... Dealer says about $600 for the fix, but $93 just to diagnose... It's probably better that I pay the $93 to at least have a 'Yota tech check it with their scanner? I have a copy of the mechanic's book which is outrageously long, and they actually seem to have to do a lot to diagnose this problem....
There is also a lower ball joint recall campaign going on since 2005 which I was unaware of but doesn't effect my '01. I called dealer and had them run VIN and said it didn't apply.

 

[Rock Slide]

Appears I'm 3rd in line...my 4Runner's CEL is also on for a P0446 code. Did buy a new gas cap from the dealer for $15, but no such luck clearing the code. (Didn't think it would, but it was worth a shot.)

Like said above, it may be a bad Charcoal Canister (repeatedly overfilling your gas tank can cause gas to overflow into the canister causing it to fail), a hole in one of the hoses in the EVAP system, or 1 of 3 VSV switches (vacuum switching valve) that have gone bad (2 are under the hood and 1 is mounted at the canister).

I'd rather fix the problem myself as I hate to pay the dealer for anything, but it may come down to that if I can't find the cause...

Oh and BTW, here's the list of possible causes that throw a P0446:

VSV for EVAP
VSV for vapor pressure sensor
open or short in VSV circuit for EVAP
open or short in vapor pressure sensor circuit
vapor pressure sensor
problem in any of five vacuum hoses
charcoal canister leaking/damaged

If freeze frame run time is <200seconds trouble is likely in the VSV for EVAP, canister, or sensor. There is a lot of checking of voltages, hose connections, electric connectors, etc. as per the FSM to be done before throwing expensive parts at this.


Good luck. Let me know if either of you find your problem area!

 

[Terrapin]

For me, the dealer did a full diagnostic test and said the entire system was fine and defaulted to a loose gas cap. He however did say that P0446 is particularly hard to diagnose. That didn't leave a warm, fuzzy feeling with me.

So far I have driven about 25 mi with no CEL.

I'm skeptical since I reset the codes myself after it popped the first time and it popped back on after about 250mi.

I reset the CEL the first time by unhooking the battery - maybe that didn't truly clear the codes.

Will keep you guys posted. Good luck with yours. If the CEL didn't deactivate the TRAC and VSC, I wouldn't really care that much (until the next emissions check that is!)

 

[Rock Slide]

You're correct in clearing the code by disconnecting the neg battery cable. You can also have your local auto parts store clear the code for free w/ their OBDII scanner.

I've cleared my code both mentioned ways, but the code returns every 4-5 days. It's just plain annoying...

 

[Terrapin]

It was good while it lasted..the CEL came back on today after about 250 mi. I knew it wasn't the gas cap.

I'm bringing it back in Tuesday and I'm hoping they can nail it on the 2nd try. I get worried about them throwing parts at something they can't truly diagnose.

I wouldn't care, but it shuts down the VSC and TRAC whenever the CEL light is on (plus, won't pass NYS inspection next January!)

We'll see...

 

[01sr54x4]

Hell, I don't get 250mi between the lights going off after I reset them! Maybe consider yourself lucky? Did you pay them to diagnose the problem initially or did they just assume it was the gas cap? It would be great if it was such a quick fix but after reading so much it's doubtful. Keep us all posted after Tuesday. I know I want to know since my lights are still on. A little hesitant to pay...

 

[Terrapin]

I did pay for the diagnosis, but they said it would be no charge to diagnose if the light came back on. That immediately told me they were not confident in their solution.

Will keep you posted

 

[Terrapin]

Well I had my follow up appointment this morning. They said the VSV was sticking. I'm thinking that they still really don't know...why couldn't they tell me that the last time instead of blaming it on a loose gas cap???

Anyway, they wanted to replace the charcoal canister for $400 + labor. I opted for them replacing the VSV only for $63 + labor instead. Hopefully that will be the fix. If that doesn't work, then I'm buying a scanner and shutting off the CEL by myself since I'm getting 250 - 300 mi between the light popping back on.

Will keep you guys posted on this one.

 

[01t4rnr]

Well I had my follow up appointment this morning. They said the VSV was sticking. I'm thinking that they still really don't know...why couldn't they tell me that the last time instead of blaming it on a loose gas cap???

Anyway, they wanted to replace the charcoal canister for $400 + labor. I opted for them replacing the VSV only for $63 + labor instead. Hopefully that will be the fix. If that doesn't work, then I'm buying a scanner and shutting off the CEL by myself since I'm getting 250 - 300 mi between the light popping back on.

Will keep you guys posted on this one.

I guess im just cheap , ive read so many posts on this and other forums about clearing this code then several hundred miles later it comes back up, even after canister change, VSV, gas cap, etc. Ive got the same code but my truck runs fine and ill be damned if im throwing money into something blindly just for emissions. I pulled the bulbs out of my dash, out of sight , out of mind :rocker: Good luck man, i do hope you find a fix but i give up

 

[Rock Slide]

I got a used working VSV switch from a member of YT for less than nothing. This past Saturday, I installed it (which BTW is a PITA to do if your bolts are as rusted as mine) and reset the monitors w/ the drive pattern instructions.

I hope this switch clears the code as my CEL comes on every 200-250 miles or so too. You also have 2 VSV switches in the engine bay that can go bad, but I've heard that's very uncommon.

Chances are if the code returns and all 3 switches are good, then a new (or good used) canister is the only fix. I'll find out myself real soon as I do about 250 miles a week.

 

[Terrapin]

Unfortunately New York does an emissions check...so I need that damn light to be out!

That plus once the CEL is on, the VSC and TRAC is turned off. Another thing that I'd like to have in working order before the New York winter. PITA.

Good luck rock slide.

 

[01t4rnr]

Unfortunately New York does an emissions check...so I need that damn light to be out!

That plus once the CEL is on, the VSC and TRAC is turned off. Another thing that I'd like to have in working order before the New York winter. PITA.

Good luck rock slide.

yeah didnt think about that, we dont have inspections here in SC so didnt even cross my mind.

 

[shawnstcyr]

Stay away from the AutoZone scan check. They are wrong 50% of the time. I know this from my experience in the garages. Go somewhere where they run a SnapOn scanner, MT2500's are good. This will eliminate the guess work.

 

[Burntcreek]

New here, been lurking for awhile and thought I'd chime in. I got this code last year and my shop diagnosed it as a valve (not the VSV) on the charcoal canister. They ran some kind of chemical smoke through the system which allowed them to visually see the leak. I know they charged less than $93 to hunt it down for me, but the new canister set me back a little over $300. It's a pretty easy DIY install if your truck winds up needing one.

 

[Rock Slide]

Update - I replaced my VSV switch at the charcoal canister and my CEL came back on a week later. I've tested a few more possibilities, but everything has checked out okay.

Sometime later this week, I'm going to have my dealer see if they can find the problem before I buy a new canister (no point in throwing money at the problem, if the canister's not the fix). Fortunately, my dealer said they'll first run a few tests for me free of charge. Hope they'll find the root of the problem then. Otherwise, I'll just pay for a diagnostic fee and find it that way. That's cheaper than a new canister anyway.

What a bothersome code...

 

[01sr54x4]

I haven't updated in a while, but I thought I'd let everyone know: my CEL went off on its own about 600 miles ago. Didn't disconnect the battery, no popping any problem/idiot lights out, nothing like that. I've been reluctant to tell anyone because everytime I do the light comes back on! At least 600mi and counting, we'll see how long this lasts. Sometimes charcoal in the canister blocks a line or valve and it can clear itself, lets hope that was the case!! Hmm, I lied... Posted above ealier in the day, but the mileage in incorrect. It's actually been 928 miles!

 

[Terrapin]

That's good news 01sr5. rare, I'm sure. I think I'm about 260 mi w/o CEL (not sure how many drive cycles...I only drive the t4r on the weekends). I'm coming up on about the same mileage that it popped back on last time ~275. I've got my fingers crossed that the VSV was the fix for me, but I almost expect that it will.

 

[Rock Slide]

Well, just found out the CCV switch under the hood was bad, thus throwing the CEL. New switch will be here Tuesday. Just glad to know it was not my canister that had gone bad.