P0420 and P0430
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Cadillac STS Forum - 2005 through 2012 Discussion, P0420 and P0430 in Past Cadillac Vehicle Discussion; Well was driving today and the CEL came on, scanner says P0420 and P0430 which means the cat(s) are shot. ...
  1. #1
    CadillacSTS42005's Avatar
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    P0420 and P0430

    Well was driving today and the CEL came on, scanner says P0420 and P0430 which means the cat(s) are shot. I know on these cars its a 3 way piece in the midstream, and there are cats on the manifolds. Which is bad, and think theyll give me any trouble because of my Corsa?

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    guitarocker420 is offline Cadillac Owners Fanatic
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    Re: P0420 and P0430

    idk about the corsa but there is a warranty on the cats for 8yrs 80k miles i got mine replaced for free

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    Re: P0420 and P0430

    Yea I not worried IF its covered, Im worried if they will try to BS me with the whole Corsa mod to the exhaust the failure. Corsa used to be the GM authorized system but now its Borla.

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    LAC_STS is offline Cadillac Owners Enthusiast
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    Re: P0420 and P0430

    I would guss that some dealers would and some wouldn't. I dunno.

    Have you checked your O2 sensors? It may be unlikely for both cats to go bad at the same time.

    The scan tool I got from a local auto parts store tells you the values for all of the O2 sensors. You can see which ones are bad.

    I had a P0430 and all the O2 sensors looked good and I could tell it was the cat because it said the bank 2 side cat was way under the minimum value.

    I'm not really sure on this one maybe someone else would know more but maybe it's a lot more likely for two O2 sensors to go bad than for both cats to fail at the same time.

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    ewill3rd is offline Cadillac Technician
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    Re: P0420 and P0430

    If it sets those codes then the cats are failing, did you clear them?

    Have you fixed anything else recently that might have affected the fuel mixture?

    Corsa shouldn't affect the warranty since the cats are before that, some dealers might complain but...

    Those suck to do on the V8 because you have to replace the whole manifold.
    Yes the coverage is 8/80 on Cats and the ECM.
    Be sure they replace the gaskets between the heads and the manifolds. The cats come with new donut seals.

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    Re: P0420 and P0430

    The last repair was a power steering pump about 2 weeks ago, since then I havent touched anything.
    I cleared the codes at advance auto parts (thats how I was able to pull them) but the CEL came back on the ride home, turned around to run them again and of course it was the same two codes.
    Yeah they don't look very fun to do at all, thank goodness for warranties haha.
    Thank you ewill3rd!

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    ewill3rd is offline Cadillac Technician
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    Re: P0420 and P0430

    You are welcome.
    I have had to do a few.
    XLR has way too little room to work.
    The only thing that makes it suck worse on STS and SRX is if they are AWD.

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    Re: P0420 and P0430

    Ummm well mine is a 1SG AWD STS4 so the tech probably wont appreciate me too much...
    I'll have to bring in doughtnuts that day.

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    ewill3rd is offline Cadillac Technician
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    Re: P0420 and P0430


    It's just a drag to have to work around the front diff.
    He will live, don't expect to wait for it though.
    Warranty time is over 6 hours on that job and they might not have parts.

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    Re: P0420 and P0430

    Update:
    Took it in two days later, new cats. No questions or even mention of my Corsa, they also noted my torque converter shudder and had to order that one, so looks like I'll be returning again soon.
    Thanks again ewill3rd.

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    ewill3rd is offline Cadillac Technician
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    Re: P0420 and P0430

    You are certainly welcome, I think I did the easy part

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    Re: P0420 and P0430

    What options do I have if I am past warrenty on the cats? I am currently getting the p420 and p430 codes and have been for quite some time now, the o2 sensors are fine, the dealer told me $1900.00 to replace them about a year ago.
    What about cutting the old cats off and have a muffler shop put on a couple of new hi flow cats?
    Also the radar unit on the 1sg, have you had or herd of those having to be replaced, mine keeps saying clean radar and ive cleaned it thoroughly and removed the front grill and tested it without grill on with same results.
    What would it run to have the dealer realign the radar unit? approx??
    Thanxx

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    EChas3's Avatar
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    Re: P0420 and P0430

    I believe the cats are part of the exhaust manifold and your options are very limited.

    On the ACC, it's sure worth trying a recalibration but there have been some posts of similar trouble requiring replacement. I'd seriously consider a auto-recycler that warranties their used parts. Otherwise it's gonna get real spendy.

  15. #14
    ewill3rd is offline Cadillac Technician
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    Re: P0420 and P0430

    Angus, I'd replace with OE, but if you don't want to there might be options.
    Check with D3, it seems like they have come up with something for the V8's.
    They are part of the manifold on the N*.

    I have repaired several "clean radar" messages with an aiming procedure and have yet to replace one.
    Aiming is a real pan, probably looking at an hour plus labor at whatever your local labor rates are.

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