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.

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