2002 sts engine codes
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Northstar Engines and System Technical Discussion Discussion, 2002 sts engine codes in Cadillac Engine Technical Discussion; I have a 2002 STS, took it to Autozone and had them hook it to a computer. The car is ...
  1. #1
    kkucher is offline Cadillac Owners Member
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    2002 sts engine codes

    I have a 2002 STS, took it to Autozone and had them hook it to a computer. The car is sputtering, stalling, hard to get going and won't go very fast.

    These codes revealed themselves when hooked to the computer. P0101, P0404, P0420.

    Any ideas what these may becaused By? can I fix this myself? How much should it cost if I take to a dealership? I live in Metro Detroit area of Michigan. Thanks for anybdies help and this is a great site.

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  3. #2
    FrankT's Avatar
    FrankT is offline Cadillac Owners Enthusiast
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    Re: 2002 sts engine codes

    P0101 Mass Air Flow Sensor Performance
    P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
    P0420 Catalyst Catalyst System Low Efficiencey

    Fix the Mass Air Flow problem and EGR valve problem before proceeding with the P0420.

  4. #3
    CadillacSTS42005's Avatar
    CadillacSTS42005 is offline Banned
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    Re: 2002 sts engine codes

    you need
    A MAF
    A EGR Valve
    and a CAT

    a EGR and driving it while running like that failed the CAT, you melted it and clogged it

    your looking at at least 2 grand if you go for OEM parts

  5. #4
    FrankT's Avatar
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    Re: 2002 sts engine codes

    Quote Originally Posted by CadillacSTS2003 View Post
    you need
    A MAF
    A EGR Valve
    and a CAT

    a EGR and driving it while running like that failed the CAT, you melted it and clogged it

    your looking at at least 2 grand if you go for OEM parts
    Woowa, slow down Jason.
    I would start by diagnosing the EGR first. An EGR valve that is sticking open will change the airflow and may cause a loss of vacuum that may also set the P0101 code or a lean code.

    You are correct about the damage that may have been caused to cat, a misfire is the worse thing to put a cat through, they hate it, I have heard some case where a misfire killed a cat in less than a minute. But, if not melted or broken up they can restore itself somewhat, though the life of the cat has been shorten.

    A restricted air intake duct
    • A collapsed air intake duct
    • A misaligned air intake duct
    • A dirty air filter element
    • A deteriorating air filter element
    • Any objects blocking the air inlet screen of the MAF sensor
    • Any debris or contamination on the sensing elements of the MAF sensor
    • Any vacuum leak downstream of the MAF sensor
    • A poor vacuum connection at the MAP sensor
    • Any water intrusion in the induction system
    • A restricted exhaust system

    All of the above can set a P0101 too. One thing at a time, diagnose and check circuits before replacing an expensive part. You also might want to try and clear all codes and see what comes back.

  6. #5
    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it
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    Re: 2002 sts engine codes

    The OP needs to learn to pull and read his own codes. You don't need to go anywhere: the car will do it for you. The instructions for your '02 are at the top sticky threads in N* performance and Tech tips.

  7. #6
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    Re: 2002 sts engine codes

    and
    I'd start by cleaning the EGR valve. Instruction are in the Tech Tips section.

  8. #7
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    Re: 2002 sts engine codes

    hey im just basing it on the codes lol
    ESI confirms my diagnosis

    if the car wont run and has a SEVERE loss in power along with driveability issues and is throwing a CAT code along with an EGR code, my exhaust knowledge tends to say he melted the cat and it aint a cheap one on these cars lol

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    kkucher is offline Cadillac Owners Member
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    Re: 2002 sts engine codes

    I have been given a quote for the, P0101, $295.00 with tax any idea if the car will run if this is replaced? It sounds like to me that it's a wait and see if I damged my CAT or not. Should I suggest that the Cad. service techs should clear the codes first or will the look at me strange of I suggest that. Thanks again for all the helpful suggestions.

    Mark

  10. #9
    FrankT's Avatar
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    Re: 2002 sts engine codes

    Mark,
    Do to the fact that the car lacks power I would drop the exhaust just before the cat and see it the problem goes away, it's quick and easy. I don't think you have a bad MAF, If you had a bad MAF then after the P0101 set the PCM would will go to a default known good value and the car would run OK. A restricted exhaust system will set P0101, drop exhaust system and go from there.

    Like Jason said,
    if the car wont run and has a SEVERE loss in power along with driveability issues and is throwing a CAT code along with an EGR code, my exhaust knowledge tends to say he melted the cat
    I agree with that statment 100%

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    kkucher is offline Cadillac Owners Member
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    Re: 2002 sts engine codes

    I took it the dealership, the service guy was very cool. He is replaceing the CAT under the warranty, there is something for GM to replace within warranty under 80k miles.

    They are going try to reset codes and go from there, they seemed very cool.

    Thanks for all the input guys.

  12. #11
    FrankT's Avatar
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    Re: 2002 sts engine codes

    Quote Originally Posted by kkucher View Post
    He is replaceing the CAT under the warranty, there is something for GM to replace within warranty under 80k miles.
    Thanks for all the input guys.
    Now you are on the right track. I bet the Cat takes care of all three codes, and you are welcome.

  13. #12
    Crown Vic Owner is offline Cadillac Owners Connoisseur
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    Re: 2002 sts engine codes

    good thing on the cat.


    Honestly, the EGR CAN NOT clog a cat AFAIK.

  14. #13
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    Submariner409 is offline If it won't run, chrome it
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    Re: 2002 sts engine codes

    Crown Vic, A stuck/slow EGR valve causes a lean signal, among other things, from the downstream O2 sensors, driving the engine rich, which overheats the cat.

  15. #14
    Crown Vic Owner is offline Cadillac Owners Connoisseur
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    Re: 2002 sts engine codes

    Quote Originally Posted by submariner409 View Post
    Crown Vic, A stuck/slow EGR valve causes a lean signal, among other things, from the downstream O2 sensors, driving the engine rich, which overheats the cat.
    A bad EGR valve in these cars make the engine run RICH?


    Interesting. Most cars default to a default AFR that is not rich OR lean, just normal.

    this happens anytime the CEL is on i assume?


    So what happens if the CEL is on for something else, say, idk, TCC clutch?

  16. #15
    kkucher is offline Cadillac Owners Member
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    Re: 2002 sts engine codes

    Quote Originally Posted by FrankT View Post
    Now you are on the right track. I bet the Cat takes care of all three codes, and you are welcome.
    FrankT I see your from Michigan, where abouts? I live in Shelby Twp.

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