CEL, dealer says I need new catalytic converters

Discussion in 'General Motoring' started by Manny, Mar 13, 2006.

  1. Manny

    Manny Guest

    I have a 99 SOW with 105K miles. This past weekend the CEL came on and
    I took it to the dealer. They say they pulled code P0420 (Cat
    efficiency below threshold bank 1), and told me I need to "replace
    catalytic converters and possibly both sensors and hardware."

    I've done some reading on this topic and I have a few questions that I
    hope someone could answer. First off, I'm a bit uneasy about the
    vageness of the diagnose. It sounds like they're not sure whether it's
    a bad cat, a bad sensor, or a bad gasket. I don't want to pay $1200 for
    the job if all that's really necessary is an exhaust gasket or a new O2

    Is it normal that both cats go bad and need replacement at the same
    time? How easy and expensive would be to just replace the sensors and
    the gaskets as a first step? Does the P0420 code really mean "bad cat,
    must replace" or is it just an indication of different readings between
    the 2 sensors (which may or may not be due to a bad cat)?

    Any suggestions on how I should proceed?

    Thanks in advance,

    - Manuel.
    Manny, Mar 13, 2006
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  2. Manny

    AS Guest

    Unless your vehicle is burning oil, it is very unlikely that your
    catalytic converter is worn out.

    Try testing the O2 sensors first.

    Was the 0420 code the only one?

    Good luck!
    AS, Mar 13, 2006
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  3. I would do this incrementally I think, change front O2 first (it get's
    more heat and more contaminants if there is a headgasket leaking.).
    Reset the ECU, drive. If the CEL comes back, change the rear sensor.

    A good mechanic can test the sensors to see if they are 'lazy'. It IS
    possible to need a converter at 105K - just not likely if the car has
    had no previous 'issues' and has otherwise been well treated.

    Carl 1 Lucky Texan, Mar 13, 2006
  4. Manny

    Backfire Bob Guest

    This is SO TYPICAL of Subaru's service/dealers.
    Get a second opinion, DO NOT mention to them you have had a quote from
    another dealer.
    See if they come to the same conclusion (bet they don't).
    At 105,000 Miles the O2 sensors probably ARE dead. You can buy the Bosch
    replacements from "Autozone"
    if you have one nearby. Call around, they vary widely in price.($40 at
    Autozone/$65 at Pep Boys)
    You can do them yourself, not hard to replace just do it with the car stone
    The O2 (oxygen) sensor(s) is a good place to start.Remember to clear the
    codes after you mess with it.
    In fact.....I would clear it and see if it comes back again. Some autoparts
    stores will pull the codes for you
    for FREE. "Autozone" is one of them.
    Backfire Bob, Mar 14, 2006
  5. Manny

    Edward Hayes Guest

    IF AFTER determining that you do need a new cat consider this. Factory
    cats are expensive and one reason is that they are designed to exceed
    the 80,000 mile minimum government mandate. There are aftermarket cats
    available that are much cheaper but, probably won't last as long. So
    it depends on how long you wish to keep your vehicle. JMO
    Edward Hayes, Mar 14, 2006
  6. Hi,

    I'll attest to the possibility of a short life expectancy of an
    aftermarket cat... limped home at 3 mph and VERY hot exhaust system
    (didn't damage car, but could have if I'd had to go very far--an
    acquaintance burned up the carpet in his vehicle under similar
    circumstances) when one self-destructed and blocked the entire exhaust
    system. Factory cat is "cheaper" in the long run IME!

    Rick Courtright, Mar 14, 2006
  7. Manny

    Manny Guest

    You guys have been a great help. Thanks a lot for all the replies.
    I will try replacing the forward O2 sensor first and go from there,
    assuming I don't see any major visible damage to the cat. I haven't
    looked under there yet but I live in New England, so a damaged cat or
    exhaust gasket due to corrosion is always a possibility.

    One more question. How do I reset the ECU? Do I need to take it back to
    the dealer for that or can they do it at AutoZone? Will unplugging the
    battery reset the ECU? The dealer did reset the CEL this time an it
    hasn't come on in the 50+mi that I have driven so far.

    - Manuel.
    Manny, Mar 14, 2006
  8. Manny

    Mickey Guest

    If P0420 is the only code, my guess is the O2 sensors are OK as they
    have their own codes if they go bad.

    Not unusual that both cat converters are combined into a single assembly.

    With the miles you have on your car it is likely you will experience
    the CEL coming on and then go off again. The freq and time the CEL
    stays on will increase. That is how mine behaved and light has been
    on steady for many months until recently went off for a couple days.

    If you attempt to replace the converter yourself, it's not an
    extremaly hard job. There are a number of mfgrs now offering cats for
    the Subaru. Inquire what the length of the warranty is. Ive' seen
    some saying 25k miles and other 50k miles. Prices can run from a
    little over $200 to about $750 for a factory replacement. Again if
    you do undertake this yourself, DON'T buy a Eastern Catalytic brand.
    Not a great fit and front O2 sensor mislocated where it hits the CV
    joint. I'm still working on getting my money back on one of these.

    Mickey, Mar 14, 2006
  9. Manny

    Edward Hayes Guest

    Many: To reset the ECU, record your radio staling numbers and remove
    the negative battery terminal. Press the brake pedal several times to
    discharge the ECM fully. Wait another 30 minutes or so and push the
    brake peddle again. Reconnect the battery, start the car and let idle
    for several minutes( I don't know why). The ECU will be reset to the
    original factory specs. The ECU will start logging how you drive from
    this point on and eventually average to come up with your driving
    type. My gas mileage went down for 2X tank full before returning to my
    Edward Hayes, Mar 14, 2006
  10. Sometimes you can talk the A'zone guy into resetting the ECU (they are
    reluctant in some states due to emissions testing and especially sales
    of used cars. - maybe take him a cold Modelo Especial! If not. Ed's
    technique should work.

    a good on-line discount dealer for an OEM cat is
    www.subarugenuineparts.com Not the only place to shop - just one I have
    been happy with. Email Jamie there for any questions. She's great. AND a
    Subaru rally racer!

    Carl 1 Lucky Texan, Mar 15, 2006
  11. Manny

    Sheldon Guest

    You can also buy a code reader that will reset the CEL light for around $50.
    I got one just to keep in the car. If the light comes on at least I'll have
    an idea whether it's okay to keep driving it. The readers generally give
    you a CD or book with a list of codes. You can also find them on the Net.
    Sheldon, Mar 22, 2006
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