2005 Camry P0446

Hello,
I have an '05 Camry 2.4L with a P0446 (evaporative emission control system (EVAP) vent control circuit malfunction) and emmissions testing required in 9 days (yikes!). I want to be 100% before I fork over the money for a new charcoal canister since the solenoids are built into the canister. The problem is everything checks out w/ a scan tool. I started w/ the basics:
1. Purge Solenoid: Works
2. Vent Solenoid: Works
3. Evap self test does not complete on scan tool (autel) - it jumps out and says motor must be on etc.. even though the motor is running and all the requirements are met such as fuel level etc.. (I'm just chalking this up to scan tool compatibility for now)

I used scan tool to close off vent solenoid while smoking the system and I can watch the vapor pressure PID increase in pressure which dissipates once I open the vent solenoid so circuit control seems intact and solenoid is functional. I understand this particular code can indicate more than just the vent control but I'm kind of at a loss. I noticed I was getting some smoke out of the gas cap when smoking so I replaced it, cleared the codes and the CEL came back on - same code.

So where I'm at now is that I disconnected the vent hose which goes to a little separate plastic box then a tube that disappears up towards the filler neck area. With that disconnected I blew compressed air in that tube as well as down the filler neck just as preventative maintenance and clear up any cobwebs or anything that might be in there. Now when I smoke the system I'm not getting any smoke out of the gas cap when I remove it or from the vent but scan tool still shows complete operation and I can build pressure and release pressure bi-directionally but no smoke from the vent or anywhere. I don't know if it has something to do w/ me blowing air in those areas or not and I'm still not any closer to diagnosing the problem. My factory service manual does not contain a diagram of the evap system so I don't know if I dislodged a ball check valve or something somewhere when I blew air into the system or if this has anything to do with anything.

Any help would be appreciated.

Thanks!

Hey BrianGee! For anyone else following along, I grabbed this quote from service info for the P0446 code:

Service Information wrote: The ECM checks if the CCV is ”stuck closed”. The ECM commands the CCV to open while the EVAP VSV is open. If high negative pressure (vacuum) develops in the fuel tank and stays for more than 4 seconds, the ECM determines that the CCV remains closed despite the open command. The ECM would then turn on the MIL and output a DTC. The engine coolant temperature is not related to the output of this DTC. The ECM also has a method for checking if the CCV is ”stuck open”. The ECM commands the CCV to close while the EVAP VSV is open. If a sufficient amount of negative pressure does not develop in the fuel tank, the ECM determines that the CCV remains open despite the close command. The ECM would then turn on the MIL and output a DTC.

So like you said, this does not necessarily indicate a circuit fault, but more of a breathing problem in the EVAP system itself. You'd mentioned lacking a system diagram, so I grabbed that, too:



And while we're at it, I also found this test routine chart. :silly: This may be information overload, but I think it's really helpful to understand the testing routine (and how the PCM came to the conclusion that there's something wrong with the CCV):

Now when I smoke the system I'm not getting any smoke out of the gas cap when I remove it or from the vent but scan tool still shows complete operation and I can build pressure and release pressure bi-directionally but no smoke from the vent or anywhere. I don't know if it has something to do w/ me blowing air in those areas or not and I'm still not any closer to diagnosing the problem.

Is it possible that, during this particular test, your smoke machine was generating pressure but not producing smoke? That'd explain why you were able to build pressure in the system, but didn't see smoke anywhere.

Tyler, thank you! Can I ask where I can find this info online for future reference? My factory manual does not have the info you provided.

My smoke machine was definitely putting out smoke,checked it multiple times but I think I found part of my problem.

I wasn't sure what the little black plastic box was on the vent piping so I removed it to get to the actual vent port on the canister and it became obvious that it was a filter. A little dirt came out of it when I pulled it so I spent a good 15 minutes blowing it out, tapping it to break up more dirt, blow it out again - over and over. it had a lot of dirt/dust in the filter. I think when I blew air down the filler neck I might have blown dirt into the charcoal canister. I just completed a 2 hour round trip this morning and the CEL didn't come on so hopefully I can run to the DMV and pass emmissions tomorrow morning which will buy me 2 years until I have to deal w/ it again. But what is still not answered and confusing to me is how I'm filling up the entire canister and gas tank w/ smoke but when I open the vent I'm only getting the faintest whisp of smoke, nothing consistent now. If I pull the purge line at the canister smoke pours out so I know it's getting all the way to the canister .Yet scan tool shows pressure basically getting dumped out instantaneously when I command it open. Pressure is being relieved somewhere but not smoke LOL! Like I said it would pour out pretty good prior to me blowing air down the filler neck. I pulled the back seat to make sure there were no leaks at the fuel pump. Nothing. I figure at this point I'll definitely need a canister down the line.

BTW, thanks for the diagram(s). I've downloaded them to stick in my repair folder. I know pulling up diagrams and posting them takes quite a bit of effort so wanted you to know that I appreciate that!

BrianGee wrote:

BTW, thanks for the diagram(s). I've downloaded them to stick in my repair folder. I know pulling up diagrams and posting them takes quite a bit of effort so wanted you to know that I appreciate that!

No problem! Fortunately, Toyota is usually pretty good about providing useful system description and operation info like the diagrams above. Not all manufacturers make it that easy. I like to provide those both for you, and for anyone else with similar problems that might happen across your thread in the future.

The info I posted and more is available from multiple sources, including Mitchell ProDemand, Identifix, AllData and probably others. It's also available online from Toyota themselves, as part of their Technical Information System. The two days/$20 option is a pretty good deal, IMO:

techinfo.qa1.toyota.com/

Is it possible that some part of the vent piping is broken or didn't get reconnected? Something that would cause the smoke to vent into a part of the car you can't easily see. The rear subframe, for example. I don't know, I'm just speculating. :silly:

But hey, the code hasn't reset yet! :silly: Great to hear. Since the CCV tests are run fairly early in the EVAP monitor, it's probably safe to say the ECM has tested the CCV at least once and liked the results. Let us know if you pass emissions.

Yeah, everything is connected up. No smoke anywhere. Even used a laser to help w/ visibility. Smoke absolutely POURS out of the evap line when I disconnect from the canister.

The IM monitors all show complete and I'm not pressing my luck by filling up the tank before the emissions test since I know it needs certain parameters in order to do the test and maybe w/ the tank mostly empty it doesn't want to do another test until the fuel level is more full. I don't know but if it buys me time that would be good. I don't have a lot of time in between now and the testing deadline and I don't want to be a parts changer and throw a $300 canister at it until I can be at least 99% sure it's faulty. I'm hoping it was just the filter which I cleared up. I'm not trying to skirt the emissions laws just need to get this passed for now which will buy me more time in order to make the repairs at my leisure w/o being hit for late fees.

Thanks again. Will post my emissions pass/fail tomorrow LOL!

Passed