Asking for a litte, off topic help

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KWS - 13 Aug 2005 07:44 GMT

I have to admit that this is not about the Miata, but this is one of the
better newsgroups for information. So I hope nobody minds that I ask.

We are considering buying a car that has the "check engine" light on.
Anticipating that this might be the case when I went to look at it, I
brought the handy code scanner with me.

The scanner said o420. The code description is "Catalyst System Efficiency
Below Threshold (Bank 1). What I have been able to determine, so far is that
either:

1. The downstream O2 sensor is misreading the output of the catalytic
converter or
2. The catalytic converter isn't doing it's job properly, which the O2
sensor is correctly reporting.

The car is a 2000 Mazda Protégé with about 115K miles on it. Thanks in
advance.

Ken

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Dale - 13 Aug 2005 14:19 GMT

it could be the O2 sensor most times they do give reading i had it done
to me twice in my Mustang
at 115 i would not think its the Catalytic its still young and has lots of
time left lol

>I have to admit that this is not about the Miata, but this is one of the
> better newsgroups for information. So I hope nobody minds that I ask.
[quoted text clipped - 17 lines]
>
> Ken

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KWS - 13 Aug 2005 18:02 GMT

Thanks, Dale.

> it could be the O2 sensor most times they do give reading i had it done
> to me twice in my Mustang
[quoted text clipped - 22 lines]
> >
> > Ken

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Leon van Dommelen - 14 Aug 2005 01:00 GMT

Note however that various engine problems may have caused a premature
demise of the cat. I would take out the cat and check whether you
can see through it. If it is like the Miata, spray WD-40 onto the
bolts the day before.

Note that 4-wire O2 sensors are not that cheap, nor aftermarket
cats, at least for the Miata, that expensive.

Leon

>Thanks, Dale.
>
[quoted text clipped - 27 lines]
>> >
>> > Ken

Signature

Leon van Dommelen :) Bozo, the White 96 Sebring Miata .)
rammm@dommelen.net http://www.dommelen.net/miata
EXIT THE INTERSTATES (Jamie Jensen)

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KWS - 14 Aug 2005 03:42 GMT

Thanks for the help, once again, Leon.

What I will likely do is (the easy thing, of course) simply change out the
downstream 02 sensor. The logic behind this is pretty much what I mentioned
in the original post. It might be simply reading good emissions incorrectly.
The general wisdom, which doesn't make it right....it's merely wisdom, is
that catalytic converters last a very, very long time.

If it works, the first stop is a local garage for an emissions check, as the
objective is to register this out of state vehicle in California. If that is
all successful and the light comes back on again at some later date, then
I'll look at something else.

Who knows? The crazy scheme might work.

Ken

> Note however that various engine problems may have caused a premature
> demise of the cat. I would take out the cat and check whether you
[quoted text clipped - 37 lines]
> >> >
> >> > Ken

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Dale - 14 Aug 2005 16:30 GMT

don't forget after you put the new one in to do a reset so the light will
go away after you put in the new OS

I just take the batt cable off for a few mins

>I have to admit that this is not about the Miata, but this is one of the
> better newsgroups for information. So I hope nobody minds that I ask.
[quoted text clipped - 17 lines]
>
> Ken

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KWS - 14 Aug 2005 18:55 GMT

Thanks, Dale.

Ken

> don't forget after you put the new one in to do a reset so the light will
> go away after you put in the new OS
[quoted text clipped - 22 lines]
> >
> > Ken

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