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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4951
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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2004 avalon VSC, Check Engine and TRAC off lights are all

Customer Question

2004 avalon VSC, Check Engine and TRAC off lights are all on. Code p0441, p0442 and p0446 come up. According to some of the research I did, it said to replace the charcoal canister and that this repair is very expensive. What are your thoughts? I also read that it could be a faulty gas cap. I bought a $10 after market gas cap, but that did not work.
Submitted: 2 years ago.
Category: Toyota
Expert:  Toyota Service replied 2 years ago.

Hello. Welcome to Just Answer. Please allow me to assist you. My thoughts are this is not a charcoal canister issue. I so believe either you have a faulty gas cap (non-Toyota caps are well known for setting these codes), the o-ring on the original gas cap was not sealing, or you have some rust buildup on the area on the filler neck where the cap seals the tank. The recommendation I have for you on this request would be to inspect the filler neck for rust, and, if none is present, purchase a Toyota fuel cap. Have the codes cleared.

If you have any questions, please feel free to reply.

Thanks for choosing Just Answer. It was a pleasure to assist you today. I trust my input to your request is satisfactory to you and meets your expectations. A positive rating would be greatly appreciated for my assistance on your inquiry.

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Customer: replied 2 years ago.
I neglected to include the fact that the same 3 dash lights appeared 2 months ago, I brought it to my mechanic and he used an I pad sized scan tool and it came up with over 100 possibilities. After he cleared it, I bought the after market gas cap which you object to and recommend an OEM toyota gas cap. The VSC, Check Engine and TRAC off lights came back a month and a half later while I was driving. How much can I expect to pay for the gas cap? Also, I do switch between 87 and 89 octane when filling up - would this affect anything? Pardon my ignorance, but is the filler neck where you put the nozzle from the gas pump? If so, it appears to not have any rust.
Expert:  Toyota Service replied 2 years ago.

Aftermarket caps do not seal properly. They are made to fit a variety of cars. Toyota caps are vehicle specific. A Corolla cap will not fit an Avalon.

A Toyota gas cap is about 25 dollars. I recommend 89 octane for all of my customers. However, this would not cause a 440 441 446 code. The filler neck is where you place the pump nozzle. Look at the area where the cap would seal. THis would be the outermost lip.

Customer: replied 2 years ago.
If the filler neck does have rust, what should I do?
Expert:  Toyota Service replied 2 years ago.

Depends on the severity of the rust. If rust is present, this can allow the gasoline fumes to escaped from under the rubber seal of the cap. If light rust is present, fill the neck with paper towels and lightly sand the seal area to reduce the rust. If there are depressions, the filler neck needs to be replaced.

Customer: replied 2 years ago.
Does the gas cap still need to be replaced?
Expert:  Toyota Service replied 2 years ago.


Customer: replied 2 years ago.
For my knowledge, what makes you certain it is most likely a gas cap related issue? Also, assuming I try all you suggested and it still is a problem, what would be my course of action? I certainly hope you suggested works, but I just want to be prepared if it does not.
Expert:  Toyota Service replied 2 years ago.

I would be wanting to look at other causes of fuel vapor fumes being lost form the tank. This could be a leaking vacuum line form the fuel tank (there are several possibilities).

The fuel vapor must be kept form exiting the tank and entering the atmosphere. There is a sensor that measures the positive pressure in the tank. Anytime you lose the positive vapor pressure (that is the rushing noise when you take the cap off; the pressure being released), the computer turns on the check engine light to alert you of this.

It could be a crack in the vacuum switching valve, where the vacuum lines form the tank connect to the valve. Most of the time, barring no other issues, the cap is the main cause...especially non-Toyota caps.

Customer: replied 2 years ago.
If I do not hear the rushing noise you refer to upon removing the cap it could me what you just described, yes? Also, would you still recommend replacing the gas cap if I do not hear the rushing noise you are referring to?
Expert:  Toyota Service replied 2 years ago.

On a hot day, with a proper seal on the cap-to-tank filler tube, there should be a slight rushing of air as you remove the cap. If not, the tank is losing its pressure. This indicates a high possibility of a bad cap seal, rust at the neck, or another loss of pressure as described above.

Customer: replied 2 years ago.
Thanks, ***** ***** as you suggested. Do you know what an oem toyota gas cap costs?
Expert:  Toyota Service replied 2 years ago.

about 25 dollars

Customer: replied 2 years ago.
An employer of an auto zone suggested try running the tank to empty and then refill with 89 octane. He suggested this because I mentioned to him that I do occasionally switch between 87 and 89 octane. I do not like the idea and will not do it, unless you think differently. Your thoughts on this suggestion. Can switching between the two octane grades also bring about the fault codes I experienced?
Expert:  Toyota Service replied 2 years ago.
You do not have a performance issue. You have an emission issue. Octane has nothing to do with these codes.