I keep getting a P0442 code approx 3 days after getting fuel. Obviously this points to the gas cap. However, the code stays clear until I refuel and tank gets down to around 3/4. I would think that if the gas cap was the issue, it would come on again regardless of the fuel tank level?

My next option is to check the charcoal canister....but I can't find it.

Also, my air box has cracked where the two halves screw together....could this be it?

I forgot to mention....this is a 2001 Lesabre!

it should be behind a fuel filter, follow fuel lines. and the purge valve usually near it but i think on this car is upfront near oil filter. As far as your question goes, i can only speculate as u do, so not much of a help here.

there is lots of things it could be. look for a large rectangle near the tank, normally larger hose going to it. as for the waiting for 3/4 its because the limits for testing are more than 7/8 full or 1/8 from empty. another common cause is the vent valve, if you take it out it should actuate with some jumpers to a battery

Not sure which engine you have but I had the same code on my Grand Am 3400 and it turned out to be the little u shaped vacuum line on the purge solenoid had gone soft and would collapse under vacuum. I replaced it, reset the code and all was good. You might have the same problem.

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This is off my dads Lesabre. I had code PO455. I went ahead and replaced the solenoid as well.

442 is the small leak test, it runs after the large leak test which would fail if it looked like that and the small leak test wouldnt even be run

Thanks for the replies! I checked all the hoses I could find and all seem ok. The hoses on both sides of the purge solenoid seem a little loose so I played with them some. Will fill up with gas tomorrow and see if the code comes back. Just can't seem to figure out why this comes on around 3/4 tank and when once cleared doesn't come back which kind've rules out gas cap and filling neck!

like i said there are quite a few conditions that have to be met before it will try the test, fuel level, time since clear, temp, time since start, probably others im forgetting. if you are in the city and its winter it may be a month before it checks