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Toyotapro, ASE master tech
Category: Toyota
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Experience:  ASE Certified, 10+ years Lexus and Toyota Certified
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Toyota echo: trouble is not the gas cap..Haynes

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How can I personally trouble shoot an Error code P0440 on a toyota echo. I know it is not the gas cap. what resources do I need - i.e Haynes book or similiar? What typical reason for this problem in my car that has 115000 miles on it. How can I turn the light off? What will eventually happen if I do not fix it? What signs will I notice if it seems to be getting worse? this is an old car, I dont want to spend any money fixing the problem if I can help it.

Hello and thank you for using just answer!

You stated this is NOT the gas do you know this?

Customer: replied 6 years ago.
It is a brand new gass cap from toyota parts. Well, I guess I don't completely know if it is fixed because I have not had my engine light reset to off. But most of the people I have spoken with claim that unless the gas cap meraculaously just broke then it is probably something else. Will Auto Zone turn that light off for me? Or can I do it myself?

You can "clear" the code for the check engine light by disconnecting your cars battery for a few minutes to reset the computer.

A p0440 is most commonly caused by a bad gas cap, those "people" are very wrong, I replace probably a dozen caps a week for this issue, the seals go bad on them. You did do the correct thing here by purchasing a FACTORY cap, I often see people buy aftermarket caps and then keep replacing more parts after a new (bad) cap continues to leak and cause this code.

The p0440 monitor ONLY runs when the car is first started, so if the problem is now solved then the light will only go off after several cold starts show this to "pass". So in other words, clear the light, then drive the car for several days, if the problem is still present then the light should come on after cold start #2.

Customer: replied 6 years ago.


After I go through the troubleshooting of the gas cap and find out that the light is still coming on, then what next? What would be the next thing to check or replace?

I really would not worry about that until you clear the light and retest it.

The fact that you ONLY have a p0440 and not a bunch of other evap codes really narrows this down.

The items that the vapor pressure sensor monitors for a P0440 code are limited to the fuel tank (including the cap and filler neck) and the charcoal canister (and the lines running between the tank and canister).


Customer: replied 6 years ago.


What if the light does come back on after the reset. I really need to know my next plan of attack. Just tell me what I should troubleshoot next and I will accept your answer. See I dont want to keep having to ask you questions when you can simply tell me what to look for next.

Thank you for your help.

That is the beauty of this site, you can log back in and reply to me on this question at any point.

If you should have some issue again on the car really it would need to be connected to an evap smoker so you can "see" the leak. Any other issue with a p0440 leak not related to a fuel cap would be very odd and out of the ordinary so you would probably be dealing with something like a small hole in the gas tank or a hole in the charcoal canister.

Toyotapro and 4 other Toyota Specialists are ready to help you
Customer: replied 6 years ago.
OK thanks for your time!

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