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Northstar Engines and System Technical Discussion Discussion, P0420 Code in Cadillac Engine Technical Discussion; I have a 2002 cadillac deville throwing the P0420 code! I checked all o2 sensors, fuel pressure and fuel filter ...
  1. #61
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    I have a 2002 cadillac deville throwing the P0420 code! I checked all o2 sensors, fuel pressure and fuel filter everything checks ok. I resealed the intake and replaced the plenum a year befor the cat went bad. no vaccum leaks. Does any one know of a aftermartket cat and to correct part # that will work. I sorry i beleave in oem parts but I refuse to spend over $1000 on this part. I alredy tried the eastern catlytic cat It did not work, I was able to get a refund. I heared that walker and catco make good cats that will work but i need part #s. any help would be apretiated. Thanks!

  2. #62
    derone is offline Cadillac Owners Fanatic
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    Re: P0420 Code

    Hey, been there, done that. I even bought one of those 'direct-fit' cats and can tell you direct-fit don't mean sh$t. Then I found that all cats aren't the same as some would lead you to believe. I had the 420 error and I have been using the Magnaflow 46006 cat for over 40k miles with no codes. It has the 2.5" in and out connections....the 46009 has 3". Double check to see which pipe yours has, as their application chart isn't that accurate. See link for more info: http://www.car-sound.com/02product/u...alCARB/460.asp

  3. #63
    Necrosan is offline Cadillac Owners Enthusiast
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    Re: P0420 Code

    You can always cheat and install spark plug anti-foulers in line with the O2 sensors to pull the O2 sensor slightly out of the exhaust stream.
    Has worked on EVERY OBDII car I've tried it on with P0420 code.
    You can cut the catalytic converter out safely at that point.
    If you're in a state that does inspections though, be prepared to explain yourself next time they put a mirror under your car.
    Here's a link to a comprehensive post explaining this process better: http://www.solaraguy.com/viewtopic.php?f=20&t=43374
    Good luck! Saved me a couple hundred bux on a few cars I could give a rats ass less about emissions on, seeing as the anti-foulers are only about $3 for 2 of em.

  4. #64
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    Thanks! did you install it your self or did you have an exaust shop do it? looks like there is some fabrication involved! can I cut exaust flange of the old cat and have it welded to the new one! also how is the performance of the car. mines is a bit slugish at times because of the partilly clauged cat.

  5. #65
    derone is offline Cadillac Owners Fanatic
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    Re: P0420 Code

    The shop measured the length of the 46006 and then cut the corresponding length of exhaust pipe including the old cat out with a chain pipe cutter. He welded the new cat up in the empty space. Only charged $35, but it was a rural area shop. The car runs like a top, haven't had any engine/tranny issues, other than an idler pulley and leaky coolant reserve tank and leaky oil pan. Those were fixed long ago. I just replaced the rear shock mounts since the shocks were sitting way up in them...next week are the strut mounts in the front. 114k miles strong and soon firmer w/o that bobbling noise over certain bumps.

  6. #66
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    thanks man! I ordered up a magnaflow 46009 with the 3 inch inlet outlet only $189 free shipping from auto parts wharehouse. the installer cut the OE converter from the flange adaptor,welded the magnaflow up and welded a 3.0 to 2.5 reducer from pep boys to the end of the cat and insalled it in the car. car runs like a champ p0420 code gone no ck engine lamp. car has been fixed 2 monthes now. im very happy that i did not have to shell out over $1000 to fix this. next project replace front motor and rear trans mounts, not completly shot yet but starting to go bad.

  7. #67
    Doug99 is offline Cadillac Owners Member
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    Re: P0420 Code

    I had this installed on my 99 Deville last week , car runs great no codes after 300 miles -

    MagnaFlow 94009 Universal Catalytic Converter
    http://www.amazon.com/gp/product/B00...ef=oss_product

  8. #68
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    Re: P0420 Code

    Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


    No codes yet, but it started to smell like rotting eggs a few days ago

    How much time do I have, before the code pops up?

  9. #69
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    Re: P0420 Code

    Quote Originally Posted by mtflight View Post
    Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


    No codes yet, but it started to smell like rotting eggs a few days ago

    How much time do I have, before the code pops up?
    I seem to recall our old Guru mention that that was a sign of a rich mixture. Might want to check the FPR.

  10. #70
    mtflight's Avatar
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    Re: P0420 Code

    Quote Originally Posted by Ranger View Post
    I seem to recall our old Guru mention that that was a sign of a rich mixture. Might want to check the FPR.
    Thanks Ranger. I keep crossing my fingers that it's something like that or bad gas. Recently I've dealt with rear shocks, now my ac mode actuator, AC and the egg stink. I don't have any FPR symptoms (had more on the Eldo but the FPR was fine on that one), but this is so simple, I'll check it out.

    EDIT: Checked the FPR and found no leaks. Sulphur smell is not so prominent, but rather weak, possibly diminishing. It could be a bad batch of gasoline (although I only get Top Tier)?

    Any other suggestions? no codes.

  11. #71
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    Re: P0420 Code

    Try a different brand of gas and see what happens.

  12. #72
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    Quote Originally Posted by mtflight View Post
    Any reduction in performance from using the magnaflow? I am floored by the prices I've seen on the OE. Even the Walker (which is OE exhaust provider, Idk about the CAT though) is over $330.


    No codes yet, but it started to smell like rotting eggs a few days ago

    How much time do I have, before the code pops up?
    No reduction in performance! car runs like a champ! its the only cat that I know off that will pass. No tellin how long they take to set. the computer will set the code as soon as the after cat o2 sensor reads out of range indicating that the cat is no longer efficient.

  13. #73
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    I would wait till it sets a code! or If the car runs poorly to replace it.

  14. #74
    mtflight's Avatar
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    Re: P0420 Code

    Quote Originally Posted by koolfred2002 View Post
    I would wait till it sets a code! or If the car runs poorly to replace it.
    Yeah, I'm going to wait. Seems like my battery is probably going to go in a couple of months first. My yearly inspection is due by the end of this month, so hopefully no codes will be set until after I pass emissions.

    Probably too much to ask, but did you say your exhaust tone changed, or become a little more aggressive? That's what excites me lol. A video or audio clip would be great if at all possible.

  15. #75
    koolfred2002 is offline Cadillac Owners Member
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    Re: P0420 Code

    yeah it did at first thats because i had a small exaust leak at the rear were i clamped it in place.I took it to an exaust shop and had it welded. now its nice and quiet it was not real lound but had a nice performance tone. I tell u what! I cranked it up with the cat off while replacing it and it sounds like a mussle car with a performance cam and headers. But to answer ur ? is close to stock when installed correctly. If u want a nice performance sound u may wan't to look at changing the 2 rear mufflers.ck out videos on youtube type cadillac dts exaust,or cadillac corsa exaust to get an idea of the sounds.

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