Code Help P0440
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Code Help P0440 in Past Cadillac Vehicle Discussion; P0440 - Evaporative Emission (EVAP) System what does that mean? if anybody can help me....
  1. #1
    jj69 is offline Cadillac Owners Member
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    Code Help P0440

    P0440 - Evaporative Emission (EVAP) System
    what does that mean? if anybody can help me.

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Code Help P0440

    It means you have a leak in the EVAP system. First be sure that the gas cap is on tight.

  4. #3
    jj69 is offline Cadillac Owners Member
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    Re: Code Help P0440

    hmm ok i cleared the codes and did that, ill see if it pops up again

  5. #4
    jj69 is offline Cadillac Owners Member
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    Re: Code Help P0440

    No, the same code came up again.

  6. #5
    SliceOfLife is offline Cadillac Owners Enthusiast
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    Re: Code Help P0440

    Quote Originally Posted by jj69 View Post
    No, the same code came up again.
    I had the same thing happen to me after buying a new gas cap. It turned out the new gas cap was defective. There's a little (about 1/8" diameter) diaphram you can see in the middle of the cap facing the gas. If it doesn't flex under pressure from a stiff probe, it's defective. Since I only bought the new cap for the tether, I pryed the tether off and put it on my old gas cap. It' still good after about six months.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: Code Help P0440

    Quote Originally Posted by jj69 View Post
    No, the same code came up again.
    OK..........Remove the engine beauty cover. Down near the rear run of the fuel rail is a black solenoid with electrical connector and vacuum lines. That is the purge solenoid which connects to the throttlebody and EVAP canister tucked into the frame rail sort of under the driver's side rear door. This system purges trapped fuel vapor from the tank during hot highway cruise conditions. It also is part of the fuel tank pressure/vacuum sensing system.

    There should be a vacuum diagram sticker on the hood, just by the hinge on your side.

    ANY leak in this system will set EVAP codes.

    NOTE: The 2000+ Northstars move the EVAP solenoid to the rear side of the throttlebody.

  8. #7
    jj69 is offline Cadillac Owners Member
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    Re: Code Help P0440

    Oh thanks nice hints, i'll check both of those things out

  9. #8
    JP31 is offline Cadillac Owners Member
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    Re: Code Help P0440

    I'm having the exact same problem. I replaced the purge solenoid but the code is still up. I haven't cleared the codes, but it is showing up as a current code. I am looking at the vacuum lines attached to the solenoid and I think one might be disconnected. There is a T shaped vacuum line boot that has no vacuum lines plugged into one side of the T. I checked another Deville and that one had the same boot but with something plugged into all side of it. I have check around and can't seem to find any lines that look like they should be running there. Any help? jj69, any resolution?

    Thanks,
    JP

  10. #9
    jj69 is offline Cadillac Owners Member
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    Re: Code Help P0440

    no jp31, mine still running with the same code haven't had the dinero to fix it lol. but try clearing the codes again and wait and see if it pops up

  11. #10
    NHRATA01 is offline Cadillac Owners Fanatic
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    Re: Code Help P0440

    Good luck, as I've been chasing this code for about 3 years. Gas cap replacement worked at first for a few months. Then the code popped up again, along with a code that had me swap out the vent solenoid at the canister. That didn't do it. Sat on it for awhile. Car began to hard start after fill up, which lead me to replace the purge solenoid. Solved the hard start issue, but not P0440. Took a shot in the dark and replaced the $30 fuel tank pressure sensor. No luck. Lines all are good and tight. I'm down to thinking it may be the o-ring seal for the pump on the top of the gas tank. But I gave up trying. I just clear the code at each fill up, and live with the SES light when the tank goes empty.

    FYI if you need to pass OBD2 emissions, clear the codes, and keep the tank topped off for about 10-14 days prior to going in for the test, and you will be ok. The EVAP leak test doesn't run if the tank is over 85% full (or under 15% but I don't advise that!).

  12. #11
    SliceOfLife is offline Cadillac Owners Enthusiast
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    Re: Code Help P0440

    Don't give up on the gas cap yet. My code showed up a couple months after getting a new gas cap. There wasn't anything wrong with old one; I bought it for the tether. In my case, the little metal diaphram in the gas cap had failed. I went back to using the old cap, but with the new tether. Code hasn't returned in 8 months--or a year and 8 months...I don't remember...

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