Troubleshooting P0442 Diagnostic code?

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Thread: Troubleshooting P0442 Diagnostic code?

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    Lifetime Member HotRod8's Avatar
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    Default Troubleshooting P0442 Diagnostic code?

    So I have had the CEL, MIL whatever you want to call it 3 times in the last few weeks. I have checked and found codes P0442, which indicates a small EVAP system leak. This would be most likely the fuel filler cap or the fuel filler tube, according to what I have read here on TS. I have also found the procedure for testing and troubleshooting the EVAP system (EG048-04). This is a really great procedure but I don't have all the fancy shmancy test equipment that you need to perform the procedures properly.

    So what I am wondering is can I use a vacuum pump/tester to isolate the problem? Can I disconnect the line at the solenoid valve (or connect up to the test port) on the intake plenum (EVAP VSV) and apply vacuum there, while disconnecting, capping, listening for leaks, etc., elsewhere in the system? Is there a possiblility of damaging anything by doing this? What about applying pressure (a few psi) and using soap to locate the leak?

    Or should I just replace the cap, then the filler tube if the cap doesn't solve the problem? I'm not one to just replace parts without knowing what the problem is.

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    Default Re: Troubleshooting P0442 Diagnostic code?

    i would probably tighten the cap a few clicks, reset the ecu,then see what happens. then if its still the same,you may want to replace your fuel cap gasket, as alot of people have been having evap system leak codes come up due to not getting the fuel cap tight enough...just my .02! hope this helps!! let us know what happens!



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    Junior Member Pistolero's Avatar
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    Default Re: Troubleshooting P0442 Diagnostic code?

    Quote Originally Posted by HotRod8 View Post
    ...Or should I just replace the cap, then the filler tube if the cap doesn't solve the problem? I'm not one to just replace parts without knowing what the problem is.
    I'm also not one to just throw money and parts at a problem without having a strong feel for what might actually be wrong. But, this was my approach to this situation when my '03 recently began to throw the P0442 code every couple of days. Since my gas cap had stopped turning past the 1st click, I figured that I'd try that before I sprung for a $125 filler tube. No more codes. The '03's allegedly are known for having a defective filler tube, but I'm hoping that mine doesn't develop that problem.

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    Lifetime Member HotRod8's Avatar
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    Default Re: Troubleshooting P0442 Diagnostic code?

    Quote Originally Posted by Pistolero View Post
    Since my gas cap had stopped turning past the 1st click,
    That's exactly what mine is doing. I don't know for sure that it ever turned past one click. Are you certain that your's used to turn past one click? I have always been in the habit of turning it until it clicks once and that's it. I actually bought a locking gas cap yesterday, figured I might as well upgrade that and hopefully rectify the CEL at the same time, if possible. The cap that I bought is not right, I have to go back today.

    Just out of curiosity does is your cap threaded like this one:
    MotoRad Part Information(This is what they sold me, supposed to fit an '03)

    ...or does it have two little "nubs" like this one:
    MotoRad Part Information(This is what my old one looks like, this is supposed to be for an '04, but crosses to the Stant 10509)
    Last edited by HotRod8; 04-19-2007 at 03:45 AM. Reason: Added a question and links to fuel cap photos.

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    Veteran Member shall36's Avatar
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    Default Re: Troubleshooting P0442 Diagnostic code?

    I posted a thread on this topic showing the defect in the filler tube o-ring sealing surface. You will probably temporarily resolve the problem by replacing the o-ring on the gas cap. Of course, 3 years is a heck of a temporary fix. The proper fix is to replace the fill tube.

    A fresh O-ring will fill in the uneven sealing surface on the fill tube. As the o-ring ages, looses elasticity, and flattens, the o-ring cannot compensate for the uneven sealing surface and you get the air leak.

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    Junior Member Pistolero's Avatar
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    Default Re: Troubleshooting P0442 Diagnostic code?

    Quote Originally Posted by HotRod8 View Post
    That's exactly what mine is doing. I don't know for sure that it ever turned past one click. Are you certain that your's used to turn past one click?...or does it have two little "nubs" like this one:
    MotoRad Part Information(This is what my old one looks like, this is supposed to be for an '04, but crosses to the Stant 10509)
    Yes, my old cap used to turn past 1 click. The OEM replacement cap that I bought will click as long as I continue to turn it. I thought it was odd when my old cap stopped turning at 1 click, but didn't think much about it at first. When I started to consistently get the P0442 code, I thought something might be up. The new cap has the "nubs" on the cap shaft.

    The cap problem didn't start to get persistent until the truck was 3 1/2 years old. At $18 for the gas cap vs. $125 for the filler tube, I will likely spend about $54 for gas caps before I get rid of the truck. If the intervals get shorter, I may have to spring for the tube replacement.

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    Default Re: Troubleshooting P0442 Diagnostic code?

    I have the engine maintanence light on with my 2002 Tundra. Came on yesterday. I want to buy a new gas cap and try that be4 going to dealer/mechanic. Question - can I use a non-Toyota gas cap that Pep Boys says is designed for Toyota Tundra? It is a Stant gas cap. Or must I stick with Toyota brand gas cap on this particular part? Anyone know about this?

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    Default Re: Troubleshooting P0442 Diagnostic code?

    Anyone else run into this problem? Do you just change the filler tube or the other 2 tubers also? Is it a hard install? approw how long does it take to swap out?

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    Default Re: Troubleshooting P0442 Diagnostic code?

    I've got an 03 Tundra and had a 0442 CEL in 05. Dealer did a bunch of leak/evap tests and I finally bought an OEM gas cap and poof, light gone. I got the ol' 0442 again the other day and went and bought another cap although I read with interest the filler tube issue. I think it was only certain VIN#'s if I remember right - not all 03 were affected. Anyhow, the charcoal cannister with it's assortment of checkvalves runs a good $400 at dealer and was mentioned by my mechanic as the next possible step if cap doesn't work. What is the warranty on emissions components?

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    Default Re: Troubleshooting P0442 Diagnostic code?

    I was getting codes P0441, P0442, P0443 every time the tank would reach 1/4 mark. I immediately blamed the filler tube, based on what I've read here. However upon inspection of the tube ring, I noticed mine did not have the indents that evyone said was the problem. Was completly smooth and consistent around the diameter. So, i then just bought an $18 dollar Toyota cap and 4 months now and code free. The new rubber gasket on the new cap is much softer, old one seemed hard and brittle. Anyway, for $18, it's worth a shot and couldn't hurt. Maybe the previous owner took care of the filler tube, because what i have doesn't jive with everybody else's 2003 filler tube.

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    Thumbs up Re: Troubleshooting P0442 Diagnostic code?

    Replaced gas cap for the second time since 05 and P0442 code is gone. For $22 it's a good starting point for troubleshooting this code on the 03 Tundra based on personal experience.

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    Default Re: Troubleshooting P0442 Diagnostic code?

    I just purchased gas yesterday and my 2003 Tundra just spit out the P0442 code. My question is, when I purchase the new gas cap will the check engine light automatically go off? If not, how do I accomplish this?

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    Default Re: Troubleshooting P0442 Diagnostic code?

    Quote Originally Posted by 2Poppa View Post
    I just purchased gas yesterday and my 2003 Tundra just spit out the P0442 code. My question is, when I purchase the new gas cap will the check engine light automatically go off? If not, how do I accomplish this?
    Most OBD meters will clear codes that I know of, and/or many auto parts places will loan you one to do this yourself as it's easy to do.
    OR just disconnect the battery for a few minutes I believe will do it also.

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