I hate emissions codes! P0446
 

My daughter told me the CEL was on in her 2010 Ford Fusion. I told her to stop by Autozone and have them read the codes. P0446 (Evaporative Emission Control System Vent Control Circuit Malfunction). Autozone guys says "most likely cause is the vent control valve" says a new one is $80. I tell my daughter to just drive it home it's not a major issue. I put a new $20 valve on, clear the code and send her on her way. Same day in less than 10 miles... damn CEL is back and so is the P0446 code.

I've read on many sites that gas cap is a primary cause. Problem is, this car doesn't have a gas cap and I have no idea how it actually seals. I'm going to put it up on the lift and check hose lines between the valve and the charcoal canister as well as the line on the filler neck. From there I'm lost. I know it's not a major concern but I like to have my kids cars in good working order. Friggin emissions codes!!

Maybe I'm missing something, but the car doesn't have a gas cap?

Right, if it's got an emmissions system, then it's got an ICE, and if it's got an ICE, then how does it NOT have a gas cap.

Nope. No twist on gas cap. Took me a while to wrap my head around that one too.

Holy hell I might be watching a video now that explains my problem! There's a seal that I might have to clean on the capless filler

So do we. People are not always willing to pay , what it will realistically take to truly diagnose, the problem, repair it, then verify the repair .
Quick run down, Check fuse # 23, then check for powers and grounds at the canister vent valve .
I believe there is constant battery voltage present at the can v valve( from fuse # 23 ) with the key on, then the ecm provides the ground when the solenoid is commanded on . A good scanner with bi directional controls is helpful here . Also, access to wiring diagrams
I believe , corrosion in the wire harness/ connector , near the can v valve is common , you are in the same basic climate as me, so that would be no real surprise . Look for some green powdery residue within the first few inches of the harness near the valve itself .
I actually enjoy diagnosing this kind of stuff, but it is hard to get paid for the actual time involved . I pay for access to all the wiring diagrams/repair information, , then have to actually , look everything, up, then locate components, and remove them to allow access, then connect up a scanner, volt meter, smoke machine, then listen to the customer belly ache about a 3 hour labor charge for a $20.00 part .
Or , just put a piece of electrical tape , or a picture of your grand kids over the light:)
I think I have seen this code cause some running problems, with a full fuel tank, or problems filling the tank , other than that, it is a non issue .

I go to the dealer parts counter on such items. If it’s a known problem and you have a good parts person, there’s a good chance they’ll know the fix. My old Silverado had a recurring emission issue that came up every few years. My parts guy always had the most recent gm part and would even give a printout of how to change it.

Just did the stuff in the video below. Took it for a 10 mile cruise and no CEL! I love simple fixes.
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I watched a video that went through the wiring tests but I don't have the fancy Snap on diagnostics to cycle the solenoids and verify with a test light. Luckily it ended up being an easy fix.
I read a few things where they said most common is a gas cap not sealing. I thought "well! I don't have a gas cap!" but then I came across the video I posted above and it all fell into place. P0446 without any other codes from what I've found tends to be a gas cap issue.

Nick - It seems to me the problem is corrosion on that flapper valve that the guy in the video says is dirty. He doesn't really address the root cause of the corrosion which is the lack of a spring to keep the fuel door closed tightly. Frankly, I'd be hesitant to put fuel in the car when that inlet is so dirty like at the start of the video. I'm glad I live here in So Cal so I don't have to put up with all that road salt that looks it is the actual cause of the problem.

The flap on my daughter's car was actually pretty clean by comparison to the one in the video. I should know tomorrow whether the cleaning "fixed" the problem or not. She'll be taking the car back to school. When I bought this car for my daughter and saw that design I thought "someone should be slapped" It took about 3 years for that thought to once again surface about this design. A twist on fuel cap is just so "old tech" I guess.

For what it’s worth, I have run into counterfeit purge valves before, so always consider where you buy parts and the likelihood of them being legitimate or not.

A twist on cap is just another step in assembly that they can eliminate with that system.
I would have had a hard time even buying a car with a system like that.

I gave that some thought when I paid $20 for a part they wanted $37 (the $80 part was actually the wrong part for the car by its design) for. I don't think it was the valve from what I've been reading though. The first step always seems to be "check the gas cap" and then further down it's the purge valve and only after verifying voltage and the wiring.

I honestly had no clue until, while on my way home after purchasing the car, I stopped to fill it up. I sat there with a perplexed look on my face for a few seconds when I opened the fuel door.

Does the fuel door have to be 'unlocked' or does it just open by pulling on it?

They have really run out of ways to make a car better when some engineering team designs a vagina for a gas cap.

Check the gas cap first.
Then the purge valve at the intake followed by the charcoal canister valve at the gas tank, speaking generally but the same or similar in all makes.

I am so getting closer to springing for one. Some of the vent valves are a PITA just to ohm out or put 12V to the solenoid to test.

I often find surface rust on the gas cap o-ring sealing surface on the filler neck. I stuff a rag in the hole in case of sparks, which is seldom, and use a small cup brush on a die grinder. I also use a touch of dielectric grease or Syl-Glide brake lube on the o-ring if an old gas cap but usually just buy a new one for $12.

http://forums.pelicanparts.com/uploa...1617567666.jpg

No gas cap rust problems in NorCal !

Critters chewing thru the wiring harness to the vent valve, yes.

http://forums.pelicanparts.com/uploa...1617568368.jpg

I hate them too. Usually happen right as the annual NYS inspection is due, and the car won’t pass with it on. Clearing the code just before the visit doesn’t help either b/c the computer “knows” it was just cleared and must complete a few drive cycles.
So some $300 BMW secondary air pump or the like needs to be identified and swapped out before it can get inspected. I don’t mind addressing misfire codes but the gas cap stuff gets criminally expensive on an older car.

Well! That didn't work. Light came back on this morning while idling in the driveway. Oh well, she's back at school. When she comes home next weekend I'll put it up on the lift and start checking things. I'll start with the fuse but I'd think if it's bad that it would have done it on the shakedown cruise I took yesterday.

I was waiting for this post. That code description is a circuit fault code, the pcm , is either seeing an open circuit, short, or lack of power or ground . You will find your answer by pinning out voltages at the ecm, and component .
Welcome to my world .

As I understand it, the ECM tells the solenoid valve to close periodically. So how do I go about verifying voltage at the solenoid without a diagnostic tool that can send a command to cycle the solenoid?

Voltage may be there all the time but ECM creates ground when it's to close.

There is also the purge valve probably in the engine compartment. Solenoid on that can fritz. What size engine?

P0466, yeah that’s gonna cost you extra, can you leave the car overnight ?

Vent valve circuit dude.

It says so in the description.

First find the vent valve.

Yep yep. You are correct, Sir.

Happens to be a path I have taken before, hence the critter reference, how the hell did they jump up couple feet ! Wrapped the replacement splice with black electrical overwrap in case it’s the color which caught their attention. But soldering while laying on your back was a new experience not to be repeated I hope.

4cyl 2.5L The valve I changed Is the one that goes into the intake. It's referred to as the vapor canister purge solenoid. From what I've found, there is also purge valve possibly back by the fuel tank at the charcoal canister.

The vent valve is the one in the back with a solenoid. It's open all the time to vent air after it's scrubbed by the charcoal. It closes when the system is periodically checked for no leak integrity.

I'll look and see where it is.

It looks like it's back at the charcoal canister by the fuel tank. I replaced the purge valve... not the vent valve. Friggin fraggin!

This is the purge solenoid. Suspect the one you replaced?

http://forums.pelicanparts.com/uploa...1617645036.jpg

Yep! I screwed the pooch! I searched vapor canister solenoid valve and the results only came up with the purge valve. I thought.. "must be the same thing!"... NOPE. Oh well. I found a vent valve for $58 shipped (Doorman) through ********* and another for $48 (Airtex) through stockwise auto. I'll probably order one. That way I have it on hand if there's nothing visibly wrong with the wiring.

Make sure you put it in writing !!!

I think he just did.

I usually rig up a battery with wires under the car and put 12V to the valve. They usually never click because so often the problem. Ohm meter works too. Don't know the ohms but if you touch the terminals and it says a big "1." you are getting warmer.

I'm not afraid to put my mistakes in writing. I should enter this in the mistake thread here. I know there's one somewhere.

I watched a video on testing the solenoid. They just used a 9v battery but I have a way to put 12v to it.

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