Pontiac Repair: DTC - P0442 EEC (Small Leak), vent valve, filler necks

Question
QUESTION: Hey Todd,

Great to have you back.  Hope you enjoyed your summer.

My 2001 GA (3.4L) keeps getting a DTC P0442 at the 3/4 tank level after every fill-up.  However, when I clear the code and keep the tank at the 3/4 level or less, I can run for weeks with no DTC set.  This DTC will only re-appear after I fill up and run the tank to the 3/4 level.

I replaced the gas cap and did a visual inspection of the EEC hoses.  Any suggestions?

I can't figure out why, after clearing the code, the DTC does not re-appear.  If there was a leak, you would think the next time the PCM ran the test it would fail and set another DTC.  But it won't as long as I keep the fuel level at or below 3/4.

ANSWER: Hi colin:

A 442 is a hard code to fix. it will only run the test wehn the gas tank is between 15-85%. being that the car is 11 years old Rot/rust come into play. The fule filler necks rot out on these things right under the plastic sealing surface where the gas cap goes on. I have see cnaisters start to leak where the bracket holds it onto the body and of course the lines can rot out and leak where any of the plastic lines attach to the metal. it needs to be taken to a repair shop that has a "smoke" machine they can induce a smoke vapor into the system and with the aid of a bright light the leak shows up as smoke leaking out on the spot for the leak. good luck :)


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QUESTION: Thanks for the advice Todd.

I believe the test is run during each cold start-up when the tank is in the 85% to 15% range.

But I still can't figure out why (after clearing the initial 0442-DTC) the 0441-DTC won't reappear during this 85%-15% operating range.

The 0442-DTC will only set after a fill-up and subsequent fuel run down to the 85% lever. --- Very strange.

Anyway, I'll do another visual on the items you mentioned above.

Thanks again

Answer
Your very welcome. One other thing I didn't mention to you is the vent valve it's self. in rare cases on these they will leak the valve will not seal due to insects huilding a nest in the valve or raod grim gets in them and they don't seal. Rare on these older ones but it still happens. I would really look at corrosion like I mentioned before as a factor I see your from Canada so you have winter to deal with just like I do here in NY.