P0420 - Catalyst system low efficiency
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Cadillac STS-V Series Forum Discussion, P0420 - Catalyst system low efficiency in Cadillac V-Series Forums; Anybody seen this code? Easy answers besides replacing the cats? I've gotten it maybe 8 times in 6 months. I ...
  1. #1
    cavalierz24 is offline Cadillac Owners Member
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    P0420 - Catalyst system low efficiency

    Anybody seen this code? Easy answers besides replacing the cats? I've gotten it maybe 8 times in 6 months. I clear it and it goes away, but seems to come back, especially when it's cold and I drive it hard on a short trip.

    Thanks,
    Alan

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  3. #2
    jedhead is offline Cadillac Owners Enthusiast
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    Re: P0420 - Catalyst system low efficiency

    The cats are built into the exhaust manifold. Replacement should be covered by emission warranty if you don't have too many miles. I had my bank 2 manifold replaced under warranty.

    Bob

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    1madstsv is offline Cadillac Owners Connoisseur
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    Re: P0420 - Catalyst system low efficiency

    You can find a car tuner in your area to tune them out but over time you will loose power because their is a problem. That is what I did then re dynoed the car 4 months later and lost 10rwhp. Now I'm cat less and car runs great hopeing to re dyno soon to see what the gains are. Very easy to do but you still need a custom tune after our you will be in worse shape than now. Ryan

  5. #4
    jmak135 is offline Cadillac Owners Member
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    Re: P0420 - Catalyst system low efficiency

    p0420 is a very common code now for many vehicles it is a cat converter below threshold meaning that the cat is not doing its job properly it should be covered 8 years 80k on emissions also you can re ignite the cats by doing a burn off procedure you would disable cyl 1 and 2 ignition coils and run engine at 2500 to 3000 rpm for 3 min this will clean any impurites out in cat and possibly fix problem just did a subaru about a month ago and also a toyota 4 runner no cel since no p420

  6. #5
    cavalierz24 is offline Cadillac Owners Member
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    Re: P0420 - Catalyst system low efficiency

    Thanks all for the help. I'm at ~74k, so luckily I'm just under the emissions warranty it seems. I'll make an appointment with the stealer next week and hopefully can actually get something fixed under warranty for a change.

    -Alan

  7. #6
    hubbel is offline Cadillac Owners Member
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    Re: P0420 - Catalyst system low efficiency

    I have had to replace the left Cat which happens to be one piece with the exhaust manifold with 2300 miles in 2006 and now the right one acted up and has now been replace at 16,500 miles under the emissions extended waranty!
    Wonder these little cats have such problems??

  8. #7
    cavalierz24 is offline Cadillac Owners Member
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    Re: P0420 - Catalyst system low efficiency

    Thanks again for all your help. After 2 weeks (special order part) sitting at the dealer, I got the car back yesterday. They replaced the cat / exhaust manifold (under warranty - just barely). Incidentally, when I picked it up the radio was completely off (no boot screen or anything). I couldn't get anything to happen but eject a disk. The mechanics had all gone to lunch, so I did the same. I pulled the neg. battery cable while at lunch and when I put it back on, everything was working fine. Any ideas what would have caused such a weird failure mode? Anybody else seen this?

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