2000 Camry V6: DTC P0446 - Toyota Nation Forum : Toyota Car and Truck Forums

93celicaconv · 03-15-2010, 04:34 PM

A friend of mine has a 1999 Camry V6 with the CEL on (sorry about the thread title- my error). DTC code is P0446 (Emissions Vent Control Circuit). He had it for years.

I got to work on it late last November. I cleared the code and asked him to let me know how long before it comes back on. The next day, after a couple of short trips, it was back on.

A week later (early December), I tested the VSV underneath the car, towards the trunk, by the fuel vapor charcoal canister. It wasn't clicking or switching vacuum when applying battery voltage to it. Found one in a salvage yard that did function properly when tested with battery voltage, installed it, cleared the code. He ran it a couple weeks this time, with various length trips, put on over 200 miles, and after that, it came back on again.

So I know his old VSV probably was defective a long time, and was hopeful the working one would solve the problem, and while it made a significant difference in how long it took before the CEL came back, it did come back. And he has been driving it with the CEL on steady since early November (it hasn't gone out since). I haven't check what code is on now, but I have a very strong feeling it is still the P0446.

I do have a complete fuel vapor charcoal canister assembly from a salvage 2000 Camry that was in a front end accident. Not sure if I should remove his entire fuel vapor charcoal canister assembly and put in this salvage one or not (looks like a fair amount of work).

Anyone have any good ideas at this point?

hill8570 · 03-15-2010, 05:22 PM

At the risk of being accused of blowing you off, I'd suggest searching this forum for P0446. Fixing this DTC has driven a number of people completely mad, so reading some of the longer threads will at least give you a hint of what you could potentially be looking at.

ajkalian · 03-15-2010, 07:57 PM

My 2 cents, just replace the whole canister assembly. I screwed around with mine trying to fix the VSV and the CEL light just came back on. Like you I got one from a junk yard, swapped it out, and haven't had a problem for over a year. It came out of a Japan model but it worked fine in my US model. Ramps are real helpful to get the car up in the air, but be careful when driving onto the ramps. I drove off mine once, no fun.

There's only 2 bolts that hold it in place, and a couple of hoses. But be warned the front bolt is a real PITA to get back in.

Once I got the canister out I found out both switches were bad, the diaphragm thingies were bad, and I'm guessing the charcoal in the canister was shot as well. While I had the canister out, I replaced the lines I could get to, with new hose. I figured while I was in there it would be a good time to do it.

If you price out the two switches and the canister at the dealer, you will fall off the floor at what Toyota want's to charge for that rats nest of hoses and rube goldberg plumbing.

93celicaconv · 03-15-2010, 09:22 PM

Thanks, Ajkalian. I actually got the fuel vapor charcoal canister and all the plumbing on the outside with it, including the VSV and a vapor pressure sensor. Were those the 2 switches you said were bad on yours (VSV & vapor pressure sensor)? How can the charcoal in the canister go bad? And how did you test your diaphragm thingies to know they were bad? I'd just as soon test what I can to make sure I'm not putting something bad back in! I know the VSV on this salvage fuel vapor canister assembly works, but I don't know how to test the rest of it.

***fenixus*** · 03-15-2010, 09:32 PM

just my 2 cents.

http://www.camrystuff.com/manuals/Gen4/Diagnostics.pdf, page 129 for details and parts checking order.

Quote:

Trouble area:
-Open or short in VSV circuit for vapor pressure sensor
-VSV for vapor pressure sensor
-Open or short in vapor pressure sensor circuit
-Vapor pressure sensor
-Open or short in VSV circuit for EVAP
-VSV for EVAP
-Vacuum hose cracks hole blocked damaged or
cracks, hole, blocked, disconnected ((1), (4), (5) holed (6) and (7) in fig. 1)
-Charcoal canister cracked, holed or damaged
-Fuel tank over fill check valve cracked or damaged

***JohnGD*** · 03-15-2010, 10:09 PM

That generation of Camrys uses a then new design of canister, and many were defective. There were some bad parts like some kind of one-way valves inside and also the charcoal can disintegrate and send charcoal powder all over the evap system. Toyota had a TSB on this.

In the terminal stage described by the TSB you had to replace rubber hoses and blow out all the evap lines.

If you already have the canister and surrounding plumbing I'd go ahead and do it. I think Haux here might have done the VSV recently not sure if he's changed the canister.

As far as the vapor sensor it's like the MAP. Except you're not supposed to pull more than a few in/Hg of vacuum in testing or it can get damaged -- something of that sort.

Quote:

Originally Posted by 93celicaconv

Thanks, Ajkalian. I actually got the fuel vapor charcoal canister and all the plumbing on the outside with it, including the VSV and a vapor pressure sensor. Were those the 2 switches you said were bad on yours (VSV & vapor pressure sensor)? How can the charcoal in the canister go bad? And how did you test your diaphragm thingies to know they were bad? I'd just as soon test what I can to make sure I'm not putting something bad back in! I know the VSV on this salvage fuel vapor canister assembly works, but I don't know how to test the rest of it.

93celicaconv · 03-16-2010, 07:07 AM

Thanks, JohnDG & Fenixus, and all who have provided input thus far. The PDF on the diagnostics will come in very handy. I'm hoping there is no difference in the parts or the dianostic steps between a 5S-FE engine (which is what the PDF is based on, from what I can see) and a 1MZ-FE engine (which my friend has). Looks like this will take a lot of diagnostics to make sure the problem causing P0446 is resolved once and for all.

JohnDG, or anyone else for that matter, is there a way I can get to see the Toyota TSB on this issue for 1999 Camrys? That may be more specific on the exact problem I am trying to resolve.

ajkalian · 03-16-2010, 07:26 AM

Quote:

Originally Posted by 93celicaconv

JohnDG, or anyone else for that matter, is there a way I can get to see the Toyota TSB on this issue for 1999 Camrys? That may be more specific on the exact problem I am trying to resolve.

You can find the Technical Service Bulletins here:

http://www.camrystuff.com/manuals/Ge...neous/TSBs.pdf

Might be a good idea to go to http://www.camrystuff.com and download all the manuals for the Gen 4 you are working on. They are great to have around that's for sure.

***fenixus*** · 03-16-2010, 09:11 AM

all gen4 camry manuals (for both engines) are here:
http://www.camrystuff.com/index.php?page=Gen4_Manuals

usually there is section for either engine within same manual, not sure why diagnostics were for 5s-fe. if 1mz-fe has no separate section then it should be same/similar. also check out other manuals as suggested above (some are separate for i4 and v6), they cover other technical steps when disassembling, checking and assembling all parts of car. SFI covers the whole Sequential Fuel Injection system for both engines, other names are pretty self-explanatory.

post back here if you need further help, i'm sure someone will chime in to drop some useful info.

good luck!

93celicaconv · 03-19-2010, 01:40 PM

Thanks, everyone, for all the help. I did some diagnostics in the engine compartment area, and the EVAP VSV was functioning normally. And when that VSV was operating, it was drawing a vacuum from the fresh air line connected at the air filter box (when I disconnected it and dead-headed it with a vacuum gauge. So I know all the long lines are connected and clear.

I decided, since I had the complete charcoal canister with all the plumbing from a 99 Camry that looked real good (except for the front end collision that put it in the salvagae yard). I had to lower the rear suspension crossmember to get enough access to disconnect hoses & wiring and get the charcoal canister out. After checking to make sure the VSV on the charcoal canister worked (for the vapor pressure sensor), I put everything back together, and ran it for a test. The ECM went through one complete run of all its diagnostics and no codes came through (either current or pending). So maybe this time we got it.

If you followed this thread all the way through, you will know I replaced the charcoal canister VSV once before due to testing the original and finding it not working. The salvage VSV that came out with his original charcoal canister, upon removal, tested good. So I'm hoping the problem was either with the vapor pressure sensor or the charcoal canister itself became defective. Time will tell, but so far, so good.

Again, thanks everyone for your help. It all came in very handly.

haux · 03-19-2010, 02:27 PM

Replacing just the charcoal canister VSV for my 2000 Camry fixed the P0446.

Later on I also replaced the canister, taken from a low mileage vehicle. Not sure if that had any benefit.

93celicaconv, going by your last post, it doesn't seem like you really changed anything this last time. Since the code hasn't come back, are you thinking maybe something wasn't hooked up correctly the first time?

93celicaconv · 03-19-2010, 04:13 PM

First time I only changed out a bad charcoal canister VSV for a known good, used on. After about 200 miles and about 2 weeks, the CEL came back on with a P0446 again.

This time, I changed out the entire charcoal canister and all it's plumbing (VSV, vapor pressure sensor, and all the small canisters outside of the charcoal canister). It was from what appeared to be a lower mileage vehicle, but I couldn't tell with it being in the salvage yard and the instrument cluster doesn't read miles w/o power.

So what I'm thinking is the original vapor pressure sensor or the charcoal canister itself was bad, besides the original canister VSV, after being operated a year with the check engine light on. I'm more leaning on the vapor pressure sensor, but I don't have a good way to test it, so I just can't be sure. I think the owner will have to run it a month or two without a CEL and the P0446 DTC to ensure the problem is fixed though.