Troubleshooting P0442 Diagnostic code?

[HotRod8]

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.

[tacomaman06]

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!

[Pistolero]

Originally Posted by HotRod8

...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.

[HotRod8]

Originally Posted by Pistolero

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)

[shall36]

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.

[Pistolero]

Originally Posted by HotRod8

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.

[helloernesto]

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?