Getting a P0420 code
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2004-2007 Cadillac CTS-V General Discussion Discussion, Getting a P0420 code in Cadillac CTS-V Series Forum - 2004 - 2007; Had the check engine light come on the other day and i'm getting the p0420 code, Car has no mods. ...
  1. #1
    KING03 is offline Cadillac Owners Member
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    Getting a P0420 code

    Had the check engine light come on the other day and i'm getting the p0420 code, Car has no mods. Can it just be failed cats?

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  3. #2
    CancerJCC is offline Cadillac Owners Connoisseur
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    Re: Getting a P0420 code

    Quote Originally Posted by KING03 View Post
    Had the check engine light come on the other day and i'm getting the p0420 code, Car has no mods. Can it just be failed cats?
    Yeah or just a failed o2 sensor which are a lot cheaper. How many miles and what kind of driving do you do with it? (I.e short trips to the store or long trips where everything comes up to temp).

    I would start at the rear o2's first if they are original with any kind of mileage then go from there.

  4. #3
    KING03 is offline Cadillac Owners Member
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    Re: Getting a P0420 code

    Well i just bought the car a couple of weeks ago with 74,000 miles. I dont drive it hard at all. I called the dealer and they said since its under 80,000 they will look at it and if its the cats they will replace them for free, but if its not i will have to pay the 125 diagnostic fee, so i am trying to see which is the best way to go

  5. #4
    catch2otwo is offline Cadillac Owners Fanatic
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    Re: Getting a P0420 code

    My car had 58k miles when I bought it earlier this year. Same CEL popped up. I had scanned at home first and then brought the car to the dealer. They diagnoised it to be a bad cat. Replaced under emissions warranty. You can always swap 02 sensors first to see if you pop a different code. If it doesnt then you know its the cat that is bad.

  6. #5
    KING03 is offline Cadillac Owners Member
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    Re: Getting a P0420 code

    when you say swap sensors, do you mean swap the before cats for the after cats?

  7. #6
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Getting a P0420 code

    You can swap the pre-cat sensor on the driver's side with the pre-cat sensor on the passenger's side. If the problem is an O2 sensor, you will get a diagnostic trouble code of P0430, which indicates the error condition has changed sides.

  8. #7
    GDPossehl is offline Cadillac Owners Enthusiast
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    Re: Getting a P0420 code

    For those beyond 80k with this code or problem, now may be a good time to go with some long tube headers with high flow cats.

  9. #8
    JFensty's Avatar
    JFensty is offline Cadillac Owners Enthusiast
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    I get that sulfur smell alot but never get a code. V has 110,000 on it and runs great. Looking into ltd and high flow cats.

  10. #9
    catch2otwo is offline Cadillac Owners Fanatic
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    Re: Getting a P0420 code

    Quote Originally Posted by KING03 View Post
    when you say swap sensors, do you mean swap the before cats for the after cats?
    Read below darkman has it right. It may be a little work but better then the dealer telling you.

    Quote Originally Posted by darkman View Post
    You can swap the pre-cat sensor on the driver's side with the pre-cat sensor on the passenger's side. If the problem is an O2 sensor, you will get a diagnostic trouble code of P0430, which indicates the error condition has changed sides.

  11. #10
    KING03 is offline Cadillac Owners Member
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    Re: Getting a P0420 code

    awesome i will try that out this week, and take it from there

  12. #11
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Getting a P0420 code

    Quote Originally Posted by KING03 View Post
    awesome i will try that out this week, and take it from there
    If you do not have one already you may want to pick up an O2 sensor-specific socket/wrench/tool which can make removal with the wire in place easier.
    Attached Images

  13. #12
    KING03 is offline Cadillac Owners Member
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    Re: Getting a P0420 code

    whats the part number on that?

  14. #13
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Getting a P0420 code

    http://www.summitracing.com/parts/WMR-W1267

    Almost any autoparts store will something simiar.

  15. #14
    RADEoN is offline Banned
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    Re: Getting a P0420 code

    darkman is my hero

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