XPost: sci.electronics.repair, alt.home.repair
From: kludge@panix.com
In article , mike wrote:
>On 23-04-2023 15:56 Scott Dorsey wrote:
>
>Could the water:gas mixture, somehow, have increased the cat efficiency?
Certainly. All that steam in there could have cleaned the converter out.
But it ALSO could have cleaned out the downstream O2 sensor. And it might
have temporarily cleaned something completely unrelated too.
>Could the hundreds of code clearings, somehow, have wiped out a buffer?
No.
>> What this means is that the O2 sensor downstream of your converter is
>> reading an incorrect value. This could mean your converter is bad, or
>> maybe that the O2 sensor is bad, or maybe that the connector is bad.
>
>When I got the Mitsubishi Lancer 2004 for $200 it had this problem then.
>I replaced the oxygen sensor (there appears to only be one upstream sensor)
>and that alone fixed the problem for the first smog about 5 or 6 years ago.
>
>There are no oxygen sensor codes.
>I need to repeat that because the oxygen sensor is not showing any codes.
You have a downstream sensor, and you know that because you got a P0240.
Check what the P0240 code means. It means that the downstream O2 sensor
is not getting the correct value. Since you aren't getting any other codes,
you can assume the upstream O2 sensor is getting the correct value, and
that the engine stoichometry is good but that the gas coming out of the
converter is not good.
That is why the P0240 sensor implies a bad converter.
How bad is the converter? Is the issue the converter itself or the
measurement? The code does not tell you. If you have a proper scanner you
can look at the actual values of the oxygen sensors. You can see that
they are in range, that they are settling in quickly, and how well they
track one another. This is how you determine whether it's a sensor or the
converter or both.
If you do not have a proper scanner you are working blind and all you can do
is measure the converter temperature with an IR thermometer and make sure
it's getting up to temperature properly. If it's too cold, it's not working.
This is a very crude measurement.
>I repeat there are no oxygen sensor codes.
>Therefore, I see no reason to suspect the oxygen sensor on a mere whim.
The P0240 -is- a downstream oxygen sensor code.
>I've noticed a lot of people replace the sensor whenever they get a code
>but that's what the tests are for on the sensor itself. If the sensor were
>bad, it would show a code of a bad input, output, or power connection.
>
>It doesn't.
The P0240 -is- a downstream oxygen sensor code.
>"The P0420 code signals a low catalyst system efficiency. This code
>suggests that the oxygen levels are below the desired threshold (Bank 1),
>which most often results from problems with your car's exhaust or fuel
>systems."
The P0240 -is- a downstream oxygen sensor code.
>I'm sure it's the cat.
>I just don't want to replace the cat.
It's likely the converter, yes, and you should almost certainly replace it,
but first verify that it's not working by looking at the actual values.
Likely it's working right now but is marginal... actual measurements will
tell you for sure.
>And, get this, it passes smog without me doing anything but clearing the
>P0420 code and letting the readiness monitors (especially for the cat) set.
Do you have the smog numbers? The numbers are also an indication of how
marginal things really are.
>> Have you considered actually finding and fixing the problem instead of
>> constantly resetting the error? You're not doing your engine or your
>> gasoline bill any good this way.
>
>There is no problem other than the cat is the original 2004 and it has low
>efficiency, and, as a result, every once in a while the P0420 pops up and
>the readiness monitor for the cat takes hundreds of miles for it to set.
That sounds like a problem to me, and one that isn't that awful to fix with
a generic replacement.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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