OEM Cat converter for '02 Impreza?

writes:

> The problem was an check engine light on (code P0420 - "cat converter
> below thershold efficiency"), and my dealer was trying to convince me
> to spend $800 on a new CAT. I can't pass the CA smog test with the
> test engine light on.


Since your original post, my 01 has thrown this very same code. And
supposedly, I have a brand new aftermarket cat that's under a year
old.

FWIW, I reset the code with the scanner I own ($100 at Wal Mart made
by Innova.) The code didn't come back for another month or so,
which gave me 3 weeks of no-CEL driving during which the counters were
also clear (i.e. would pass emissions). I think it took about a week
of driving to build up enough engine time to reset/pass the rest of
the stuff that makes for a happy emissions odbii check. It isn't
considered "clean" right after you reset everything.

Anyway, if you are blowing clean emissions, and it does just look like
a sensor issue, you can have a buddy with a code scanner reset your
code, wait a week and have them recheck to make sure all the
counters/such have gotten to their happy place, then immediately go in
and have those emission checked, and you may make it another year.

Just one option anyway.


--
Todd H.
2001 Legacy Outback Wagon, 2.5L H-4
Chicago, Illinois USA

wrote:
> On Aug 25, 5:57 pm, Carl 1 Lucky Texan wrote:
>
>> wrote:
>>
>>>On Jul 2, 1:53 am, wrote:
>>
>>>>My '02 Impreza Outback got 121,000 miles, and my local subaru dealer
>>>>has got a Cat converter check engine code reading.t. They quoted me
>>>>$850 to replace the Cat ($650 part + $200 labor).
>>
>>>>All I need is to pass the California smogs. I am not driving the car
>>>>much anymore anyway (gas prices), just keep it in the driveway for an
>>>>occasional camping trip (still cheaper than renting... provided no
>>>>major repair costs) so giving out $800 just to register the thing just
>>>>does not sound right.
>>
>>>>Goggling produced a $150 (???) "Catco" converter. Does anyone have
>>>>experience with this beast? Can I bolt it on myself to keep the
>>>>smoggers happy?
>>
>>>>Also, I am not sure if the sensor in the car gives a yes/no kind of
>>>>answer, or actually produces a real number. Meaning that if I knew
>>>>that the reading was on the borderline, can I make the car barely pass
>>>>somehow (heard some urban legends on driving on a highway before the
>>>>test).
>>
>>>Hi all,
>>
>>>I bugged you guys ~2 months ago about a cat converter error code on a
>>>'02 Impreza, and I got some very good suggestions from you.
>>
>>>The problem was an check engine light on (code P0420 - "cat converter
>>>below thershold efficiency"), and my dealer was trying to convince me
>>>to spend $800 on a new CAT. I can't pass the CA smog test with the
>>>test engine light on.
>>
>>>Well, my registration is due in 2 weeks and I just took the car for a
>>>smog test (the dealer protested, saying why bother - well, since the
>>>retests are free, why not).
>>
>>>It passed the smog test ***easily***. At idle the numbers were:
>>>14.6% CO2, 0.1% O2, 17 ppm HC, 0.03% CO, not anywhere close to the max
>>>allowed numbers.
>>
>>>So I runs back to the dealer and ask them just to replace the front O2
>>>sensor. But they *insist* on replacing the cat converter, saying that
>>>if the system says it fails, it fails.
>>
>>>So the question is - how can the cat converter be faulty if the
>>>emissions are fine? Or do the emission people and the cat converter
>>>sensor measure different things?
>>
>>>I can insist on replacing just the O2 sensor ($250 as opposed to $800)
>>>though, but at this point I don't know if I can trust them at all -
>>>unless I misunderstand something.
>>
>>There is no direct way for the OBDII to measure cat performance other
>>than comparing the upstream and downstream sensor values with ideal
>>numbers in memory.(basically) So, for most cars, it would be like trying
>>to measure one old component using 2 other old components. But a GOOD
>>shop should be able to perform tests on the sensors that would show slow
>>switching or a failed heater circuit, etc. They should also be able to
>>do a tailpipe emissions test. Basically, your dealer is either corrupt
>>or incompetent (hard to see a 3rd option here).
>>
>>This not say its impossible to have more than one bad component. Or,
>>indeed, replace one now, and need a second component replaced in a few
>>days/weeks w'ever.
>>
>>try reading a couple of articles here;http://www.troublecodes.net/articles/
>>
>>OBDII..simply explained
>>Cat. Eff. Failures
>>
>>Carl
>>
>
>
> Carl - so, would a good emission test argue against a bad converter?
>
> My other mechanic says that the upstream sensor fails statistically
> more frequently because it experiences more stress (the sensor
> generates voltage, right). I kind of buy that.

I have read MANY reports of upstream sensors failing WAY before the
downstream unit. There are probably 2-3 reasons for this in various
combination(heat, more corrosive gasses,etc.). Not impossible to have a
bad converter or bad downstream converter - just difficult for the
upstream sensor to last much over 80,000 miles or so. Could some last to
130K? probably. Some also fail at 60K or less. Especially if they have
been exposed to coolant from a leaking HG or other stresses. And it is
often a 'slow' failure. Sometimes the code can be cleared and may not
return for weeks.

There probably are some rare mechanical ways a Cat converter could be
partially clogged but still pass an emissions test - dunno - but the car
would probably have driveability isues at high speeds or under load.


Carl


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