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Old 09-23-2015, 06:09 AM   #1
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O2 Sensors replacement

I have a marginal CAT with a P0430 code and think it may have gotten plugged up after my AOS failure a 1000 miles ago.

I just ignored the Engine light hoping it would eventually improve after using some Techtron additive but it has been staying on more than off.

I have a smog due in Nov so its time for action.

I plan to run some "CRC Guaranteed To Pass Emissions Test Formula" and replace the rear O2 Sensors, plus use some MAF cleaner.

Does anyone know the Brand Model number I should use for the post Cat Sensors, and a good source?

I'm confused by the array offered online that supposedly fit as OE and range from $24-$80.

Don't want to get an inferior or incompatible part.

Ray

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Old 09-23-2015, 08:13 AM   #2
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Originally Posted by jb92563 View Post
I have a marginal CAT with a P0430 code and think it may have gotten plugged up after my AOS failure a 1000 miles ago.

I just ignored the Engine light hoping it would eventually improve after using some Techtron additive but it has been staying on more than off.

I have a smog due in Nov so its time for action.

I plan to run some "CRC Guaranteed To Pass Emissions Test Formula" and replace the rear O2 Sensors, plus use some MAF cleaner.

Does anyone know the Brand Model number I should use for the post Cat Sensors, and a good source?

I'm confused by the array offered online that supposedly fit as OE and range from $24-$80.

Don't want to get an inferior or incompatible part.

Ray
First of all, if you have a questionable cat, changing the O2 sensors is going to do nothing. What you should be doing is running a scan of the sensors on each bank to see what they are doing; one should be staying pretty much at one voltage while the other cycles back and forth in a sine wave like curve. If both sensors are following the sine wave, the cat is done and nothing is going to save it. And dumping in magic bullet fixes are not going to heal it either.
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Last edited by JFP in PA; 09-23-2015 at 08:17 AM.
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Old 09-23-2015, 11:09 AM   #3
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Since my P0430 code comes and goes, borderline, I thought that fresh sensors may be just enough to pass the smog.

I realize what you are saying is true but I need a slight nudge to pass the smog and since this has occured AFTER a major smoke fest with the AOS going out I feel that carbon from all that oil is what may be hampering/plugging my cat and sensors.

I'll check the sensor Voltage curves and see if I can confirm what is happening.

In theory the Cats should last forever if they don't get plugged, fouled or broken ceramic matrix.


I take it the upstream O2 sensor voltage would be the nearly constant voltage and the downstream following the sine wave?
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Last edited by jb92563; 09-23-2015 at 11:13 AM.
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Old 09-23-2015, 06:37 PM   #4
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Old 09-24-2015, 02:58 AM   #5
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If the sensor voltages are in the correct range, it ain't the sensors and putting in new ones will only make your wallet easier to sit on.
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Old 09-26-2015, 05:00 PM   #6
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Quote:
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I take it the upstream O2 sensor voltage would be the nearly constant voltage and the downstream following the sine wave?
Upstream following the sine wave and downstream nearly constant. If downstream is a sine wave too then the cats aren't doing the job. I think there are lots of good graphs and info in the thread jager linked.

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Old 09-26-2015, 05:49 PM   #7
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I'm in the same situation, and mine is due this month. I've read that O2 sensors that don't work properly will give you codes. Moreover, they say that if those stay within the correct voltage range (0.1 to 0.9 in this case, and downstream should try to stay at ~0.7 consistently, then they are OK. But I've also read that there are cases when O2 sensors get tired, and haven't triggered a code yet, but will affect their response time.

Anyway, you can get the Bosch ones from Amazon or ******************************** for about $80 to $100. The Universal one, which requires you to do the connector, is even cheaper at $60.

Here are the voltages for my working bank 1 and dying bank 2 cats.
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Last edited by hancock1701; 09-26-2015 at 05:52 PM.
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Old 09-27-2015, 05:18 AM   #8
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O2 sensor and other emission CEL codes are not equivalent to smog test levels. Of course, you can't pass the test with a CEL. You say that the car is on the edge of triggering a code but it still could be WAY out of compliance for the smog test (or it could be within the limits).

I would suggest getting a smog pre-test done to see where the car really stands in terms of smog compliance. Many shops will do them cheaply and don't report the results to the state DOT/MOT.

Having the actual numbers will go a long way in helping you to decide what needs to be done in order to get back in compliance (and you'll know for sure whether you a long way off or really just need a nudge to pass the test).

Knowledge is power.
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Last edited by thstone; 09-27-2015 at 05:21 AM.
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Old 09-27-2015, 06:56 AM   #9
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I'm in the same situation, and mine is due this month. I've read that O2 sensors that don't work properly will give you codes. Moreover, they say that if those stay within the correct voltage range (0.1 to 0.9 in this case, and downstream should try to stay at ~0.7 consistently, then they are OK. But I've also read that there are cases when O2 sensors get tired, and haven't triggered a code yet, but will affect their response time.

Anyway, you can get the Bosch ones from Amazon or ******************************** for about $80 to $100. The Universal one, which requires you to do the connector, is even cheaper at $60.

Here are the voltages for my working bank 1 and dying bank 2 cats.
You have a bad cat, not bad O2 sensors:




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Last edited by JFP in PA; 09-27-2015 at 06:59 AM.
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Old 09-27-2015, 09:22 AM   #10
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JFP and others are right. If your sensor voltages are in spec and your read O2 readings are sine waves instead of essentially flat, your cats are cooked.

CA no longer does a tailpipe test for '00 and later cars. To pass, your CEL must be off, your monitoring systems should be ready, and I believe you mustn't have and stored emission codes.

If you have a Durametric, check the O2 sensor voltages to confirm the problem. A few days before testing, clear CEL and stored codes. Drive the car several times until the monitoring systems reset. Then get the car tested.
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Old 09-27-2015, 02:04 PM   #11
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Used cats are not expensive and are perfectly acceptable! Just make sure they are guaranteed to be fully functional.
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Old 09-27-2015, 02:55 PM   #12
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Here is a place that sell Calif legal replacement CATs
$170 rear / $186 front

Search - 250-24647 250-24647 250-24647 250-24647 441204 441204 441204 444204 444204 444204
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Old 09-27-2015, 03:04 PM   #13
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Here is a place that sell Calif legal replacement CATs
$170 rear / $186 front

Search - 250-24647 250-24647 250-24647 250-24647 441204 441204 441204 444204 444204 444204
The problem with those is that I can't imagine them being welded in place of the pre/integrated CAT. There doesn't seem to be enough space. I had a thread recently asking about putting these universal cats in place of the other downstream cats, and move the O2 sensors, but that wouldn't work either, due to technical and other reasons too.
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Old 09-27-2015, 06:26 PM   #14
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While its true as NewArt says that used catalytic converters 'are perfectly acceptable" as a fix to a dead cat, California prohibits their installation. Here's a quote from the California Air Resources Board website:

"Information About New Regulations for Aftermarket Catalytic Converters

The ARB adopted revised regulations and evaluation procedures in October 2007 for the approval of new aftermarket catalytic converters sold in California. The requirements apply to all new aftermarket converters produced for sale or sold in California after January 1, 2009. The requirements also sunset provisions allowing the sale of certified used catalytic converters beginning July 10, 2008. This means that no used converter can be legally advertised for sale, sold, or installed in California after this date"

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