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

On Jul 2, 1:53 am, runcyclexc...@gmail.com wrote:

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.

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).