Service Engine Light Keeps Kicking On
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Service Engine Light Keeps Kicking On in Past Cadillac Vehicle Discussion; Hello all, I currently own a 2001 Cadillac Deville DTS (I know this thread is for 2006-2012) but I really ...
  1. #1
    Intro is offline Cadillac Owners Member
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    Service Engine Light Keeps Kicking On

    Hello all, I currently own a 2001 Cadillac Deville DTS (I know this thread is for 2006-2012) but I really need an answer. For a while now, after reaching so many miles of driving, my service engine light kicks on. And all of the times it says its a P0442 code, or a small EVAP leak. I've gone through a number of repairs and replacements to try and fix the problem but it keeps coming back on. Here's what I've had done since it first started:
    • Replaced the fuel filler cap.
    • Replaced the pressure sensor on top of the gas tank.
    • Smoke tested twice with no visible evidence of a leak, not in the canister or hoses.
    • Something in a loop that's suppose to open/close regarding fuel (if I heard my mechanic right, he says that's working right)
    • No leaks from fuels lines or fuel tank or anything else.

    Is there anything else that keeps triggering this code? Something I may be overlooking perhaps?

    Thank you for any help.

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  3. #2
    Superjim's Avatar
    Superjim is offline Cadillac Owners Connoisseur
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    Re: Service Engine Light Keeps Kicking On

    A small exhaust leak can sometimes cause it...

  4. #3
    Intro is offline Cadillac Owners Member
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    Re: Service Engine Light Keeps Kicking On

    Could a coolant leak cause the trigger? I ask because I've had to fill up the reservoir a number of times after it tells me to check coolant level.

  5. #4
    Henskelly1960 is offline Cadillac Owners Member
    Automobile(s): 2008 Cadillac DTS, 1986 and 1970 Fleetwood 75 series Limos
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    I had a similar issue for a while with my check engine light coming on, replaced the fuel cap several times in several months, the one I bought from Pep Boys seemed to be the best fitting/sealing one but the issue continued. Dealer did some sort of computer update that took care of the problem (or rather, the engine light comes on for OTHER problems now!). They wanted $100 for the programming which I nicely told them was way too much to pay for them to do something like a computer software update and they did it for me for $30. They did the smoke test which came back fine and thought it was the part you mentioned under the hood but when it was tested it showed perfect function, which led them to a service bulletin regarding a glitch in the computer.

    Still, it's nice to know that when the light comes on now it's because of another issue. I had the same engine light fuel cap type deal going on in my 07 Saturn Aura and ignored it, but then other issues came up and they were never addressed and the car ended up more or less done for so it was traded in for a whopping $1500 towards my DTS that Saturn was a great car when I first got it but I drive a LOT and I was glad to see it go. The only car I've owned so far that I haven't been bummed out about having to get rid of...but who's gonna miss a Saturn when you're driving off the dealer lot in a gorgeous Cadillac?

  6. #5
    Intro is offline Cadillac Owners Member
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    Re: Service Engine Light Keeps Kicking On

    So it's possible it could be a computer glitch, that thought was in the back of my head but I didn't wanna bring that to the forefront. Haha the only problem trading your Saturn for a Cadillac, you'll be paying more for parts now

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: Service Engine Light Keeps Kicking On

    Intro, remember that your 2001 DTS (Deville Touring Sedan - it is NOT a later "DTS") uses a quite different OBD system (OBD-II) from 2005 and later - they shifted to CAN diagnostics, so some info you may gain here might just be out in left field. Also, the later EVAP system is different from ours.

    You need to do a thorough diagnosis of your EVAP system, from throttlebody solenoid to charcoal canister to fuel tank....... and know that a rusted out fuel filler neck is common on Devilles. Your EVAP test port is the black line with green cap - comes from the solenoid on the TB.

    ....and it's not a "computer" (PCM) glitch. Your coolant leak has nothing to do with the EVAP system. Proper coolant level is half full, cold - shown by the FULL COLD legend and arrow molded into the surge tank. Any higher and the normal coolant expansion/contraction will blow coolant out the overflow line at the filler neck. (2001 - different from 2005 and later.)

    "Loop" - that state of engine and emissions controls monitoring determined by ambient temp and coolant temp. From cold the engine starts in Open Loop - veery little is monitored. As temp rises the systems go Closed Loop and more and more engine/emissions controls are brought into play. (Different sequence in your 2001) All emissions controls are bypassed at WOT operation.

    ..............search through Cadillac Tech Tips.

    generic diagram - YOUR EVAP system

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