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    MODEL:Cavalier ls sport
    ENGINE:2.2 dohc
    DESCRIBE ISSUE.... just got the car in trade and is giving a p0440 - EVAP system malfunction all i have access to is code reader so don't have more than this but am told this could be due to the cas cap being defective is that the major cause of this or could it be something else?
  2. p0440 is a generic EVAP system code, often other codes or issues are present.
    Do not clear/erase the code - suggest you take advantage of free scans at many auto parts stores.
    Will your code reader read ALL codes esp manufacturers specific - ie P111x?
  3. I have same scanner as AutoZone and them use it reads mfg codes too but have to look up definition of those but only codes are the p0440 twice
  4. First, try looking at the "gas cap" sealing surface first. If you see any rust on the mating surface of the gas filler tube, start there. But that is probably not the source. It would have coded a P0450 which is a gross leak or something similar, but from memory, these old cavaliers didn't go that far into the self test as of today. Best bet is to have a tech 2 and follow the pdf I will include in this post.

    A smoke machine may be needed to smoke this pesky code out.

    A common occurrence on these cars is the FTP sensor. Which means fuel tank pressure sensor. So even with a smoke machine, this may be tricky to see as a fault without a tech2 scanner.

    You need a bi-directional capable scanner for this.

    Here is a PDF chart of the steps to follow.

    A walmart code reader is only good to check the codes, without bidirectional controls, this is a code you can throw many parts at, and thousands of gas caps without any joy.

    The only thing really you can do at this point is to check for any obvious damage to the evap vacuum hoses, canister and if your any good with a battery and bat +, check to see if the purge valve or vent valve is clicking, but without a bidirectional scanner, you don't know if the PCM is commanding on or off.

    Anyway, here is that trouble shoot, and if you want, buy the tools to check that, which I highly doubt you will want to. Or send it in armed with this trouble shoot. There is no magical fix for this. Just attention to detail.
  5. Most often, the vent valve is stuck open. ANd even commanding it on or off will produce a click, but the damn thing is stuck in open, hence the smoke machine to weed that out.

    If you good with your hands, make one yourself, Not your normal DIYer type tool to make, but if you are determined enough, anything is possible.

  6. Ok..... Well the scanner you mentioned is not anything I have nor am I that tech savvy this is not a vehicle I intend to keep just not into cars being a big guy I like my truck I traded a 97 2wd Ford ranger with 313k for it that needed a windshield and O2 sensor so I think I still did ok but would prefer it to be 100% as NH anything 98 and Newer requires obd2 emissions scan for inspection
  7. To better understand this basic evap system watch this video.

  8. Update turns out my buddy had a smoke machine he made only leak in system was the purge valve by charcoal canister so replaced that and will see if light stay out
  9. hoping you see this before throwing out old purge valve.

    Try to inspect failed valve looking for charcoal preventing the sealing.... a failed canister will break up and send pieces into purge, only to cause new valve to leak....

    TIP - Do not top off tank
  10. Second that. But at least you found that that valve was stuck. Hope it puts out that evap small leak code for at least a while until something else comes up, which usually does. Ain't I the optimistic one today. Time for up beat music.

    Vacation is soon over.

  11. the purge valve casing was leaking not the canister itself this one just pops into the unibody rail appears to simply vent to atmosphere i have sold the car but guy has yet to run it but on smoke machine that my guy built that was the only issue he found
  12. Update guy finally registered car drove it short way and code came back we cleared it this time as think several things one I put new part in and only moved it 50 ft as battery had been disconnected by the shop that welded the rear unibody for me and the guy I don't think ever goes over 25mph maybe 30mph on good day