just need some points i could check, tried replacing the gas cap with no success. I am guessing from my searches it is a broad area, but looking for some helpful tips on some of the main causes. Thanks

i wrote: 0440 relates directly to the evaporative emissions system. the parts that it monitors include (from stern to stem): the gas cap, the gas fill neck, the gas tank, the gas tank pressure sensor, the vacuum lines running from the tank to the evap canister, the canister itself, the valve on the canister, the lines from the canister to the purge valve, the purge valve itself, and finally, the line from the purge valve to the intake manifold.
if any one of these 16 parts is faulty, it could trigger the 0440. the most common place to begin diagnosis is with the gas cap, as if not screwed on tight enough (by yourself or the gas station attendant) -or- if the rubber on the cap has degraded enough to not make a seal, then this code could be thrown. a gas cap should not cost more than $6-$8 at your local parts tore. next, a visual inspection of the lines to see if any are cracked, broken, kinked, or otherwise pinched off/leaking. if, after these inspections have been made and determined to not be the cause of the problem, i wold recommend getting your emissions system smoke tested.the parts after these simple diagnoses can get quite expensive depending on where you get them from, and as such, you'll only want to change the part thats causing the issue.

same problems could cause an 0442.



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awesome info, thanks so much