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Discussion Starter #41
So, is there no one who can please help a poor Subie owner diagnose the PO420 code issues from the data I've posted above? I'm at a loss as to what to do until someone can decipher the numbers. Thanks. LRV
 

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Attached are .txt files for some extended logging with BlueDriver during a long trip under freeway conditions at speed. Since BD says its best not to try to log more than 5 variables at a time, I selected groups of the variables
As there's only five parameters in each log, and each log apparently covers a different time period, it's not possible to relate a parameter in one log with another that's in a different log. When I listed the desired parameters, it was with the hope the your device can log more than just five. Have you looked at the P0420 Diagnosis thread? P0420 Diagnosis. It can provide insights into what to look for and record. This code does not have easy answers, as is evident from it's length -- almost 2000 posts.
 

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Discussion Starter #43
Plain OM, thanks for the reply. I've tried to work my way through cardoc's thread but at several points it gets too technical for a technopeasant like me. So, if my BlueDriver can really only log 5 sensors at the same time, which 5 should I select? Also, is there a particular driving situation that might be more revealing than others? I was told by my local Sub dealer senior mechanic that he prefers the data be logged while driving at steady freeway speeds and then lift off the accelerator and let the car coast slower for a bit, and then check the graphs for the delay time between when the O2 level on bank 1 sensor 2 shows in increase in O2 as compared to when the fully downstream sensor 3 shows a decrease in O2. It's the time delay that he's looking for. I don't know if he is correct, but that's what I understood him to suggest. Also, FWIW, one shop tested for exhaust leaks and no exhaust leaks were detected. Thanks. LRV
 

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As your car is CA-spec and has three cats and five sensors, the P0420 could be caused by a bad cat on one side, or both sides, or a bad sensor on either side. With only five parameters available at the same time, we can't look at all the data that might be indicative of where the problem originates.

Even for one side, I'm not sure 5 would be adequate. But to try, perhaps run two sets of two logs, one set focussing on bank 1 and the other on bank 2, with one on each side at warmed up idle for a minute or two, and one while driving steadily at a moderate freeway speed, e.g. 55 mph. So four logs in total.

In each log, include (selecting the bank specific parameters where they are different):
Sensor 1 - Equivalence Ratio
Sensor 2 - Oxygen Sensor Voltage
Absolute Throttle Position
Short Term Fuel Trim
Long Term Fuel trim

ving at steady freeway speeds and then lift off the accelerator and let the car coast slower for a bit,
That's a test of the sensor response. A bad sensor could cause the P0420 even if the cat is good. Where there's separate cats in each side, as in your case, the logs have to include the sensor and throtlle position data for both sides. So, both Equivalence Ratios, Both Oxygen Sensor Voltage, and the Absolute Throttle Position. That said, I'm not sure how reliable the result would be in this case, as well as in the other four logs. That's because in the previous logs, each line of data was 0.5 second apart. That could skew the results by introducing a delay in the data where in fact the changes are much closer together. But again, it could be tried.

I think apps like BlueDriver are good for routine monitoring and in some cases diagnosis, but in more complex situations, unless something is clearly amiss, they have their limitations.
 

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Discussion Starter #46
Just to clarify, using the BlueDriver software, my options for the O2 sensors are as follows:

Bank 1 Sensor 2 - O2 Bank 1 - Sensor 2 - Oxygen Sensor Voltage
O2 Bank 1 - Sensor 2 - Short Term Fuel Trim
Bank 1/2 Sensor 3/1 - O2 Bank 1 - Sensor 3 Oxygen Sensor Voltage
O2 Bank 1 - Sensor 3 Short Term Fuel Trim
Bank 2/3 Sensor 2/2 - O2 Bank 2 - Sensor 2 Oxygen Sensor Voltage
O2 Bank 2 - Sensor 2 Short Term Fuel Trim
Wide Range O2S - Wide Range O2S: Bank 1 - Sensor 1 - Equivalence Ratio
Wide Range O2S: Bank 1 - Sensor 1 - Voltage
Wide Range O2S - Wide Range O2S: Bank 2 - Sensor 1 - Equivalence Ratio
Wide Range O2S: Bank 2 - Sensor 1 - Voltage
Wide Range O2S - Wide Range O2S: Bank 1 - Sensor 1 - Current
Wide Range O2S: Bank 1 - Sensor 1 - Equivalence Ratio
Wide Range O2S - Wide Range O2S: Bank 2 - Sensor 1 - Current
Wide Range O2S: Bank 2 - Sensor 1 - Equivalence Ratio

I understand that Sensor 3 is the actual downstream sensor after the third cat. So, should Sensor 3 be used in any of the test runs? If yes, for both Bank 1 and Bank 2 tests? If I need to include sensor 3, should I drop out sensor 1's? Or, include sensor 1's which may mean I'll be monitoring 6 sensors instead of 5? Help. Thanks. LRV
 

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Discussion Starter #47
So, I ran some further logging this morning. Attached are txt files of each of the three logging sessions. The first was at Session 1 - cold start, idle up and then drive on city streets for:
Bank 1 Wide Range O2S: Bank 1 - Sensor 1 - Equivalence Ratio
Bank 1 Sensor 2 - O2 Bank 1 - Sensor 2 - Oxygen Sensor Voltage
Absolute Throttle Position
O2 Bank 1 - Sensor 2 - Short Term Fuel Trim
Long Term Fuel Trim Bank 1

Session 2 - warm start, drive onto freeway, freeway driving for same sensors as Session 1:

Session 3 - warm start, drive onto freeway, freeway driving for. I tried to monitor only Bank 2 sensors equivalent to Session 1, but it looks like all of the changed sensors didn't pick up data.

I did not log anything for sensor 3 in these sessions.

So, can anyone see anything particular with these data? What should I log next if I'm limited to five sensors at a time? Also, I see the time intervals to be a half second or more in some cases. Is that a serious limiting factor in diagnosing the real problem? Are shop logging equipment able to log all variables simultaneously and with much shorter time intervals? Thanks. LRV
 

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A few posts back someone suggested using O2 sensors extensions, if your o2 sensors have been off should be easy to install and you can use them easy way to "test" the cats.
I haven't looked at your last sets of data, like i told you before, the response from your back o2's indicate cats that no longer "function" up to spec. That doesn't mean they not working, many times i have seen P0420's and the cats were still doing they job ( i have a 5 gas analyzer), but because they have been poisoned or just depleted of Cerium the MIL will be on.
Its an older vehicle and hurts to spend that much on cat's, just use the extenders and see what happens.
 

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Discussion Starter #49
The extension might work, if I could only reach the downstream O2 sensor and easily remove it, attach the extension and re-install with sufficient clearance. I'm not able to do that and reluctant to ask a garage to do it. I ran some more BlueDriver logging on Friday and they are attached below. The time intervals are about 1/2 a second. Is that too much of a time interval to make the data useful? Any further interpretations? Thanks. LRV
 

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The extension might work, if I could only reach the downstream O2 sensor and easily remove it, attach the extension and re-install with sufficient clearance. I'm not able to do that and reluctant to ask a garage to do it. I ran some more BlueDriver logging on Friday and they are attached below. The time intervals are about 1/2 a second. Is that too much of a time interval to make the data useful? Any further interpretations? Thanks. LRV
There's electronic version that will mimic a good oxygen sensor waveform. I used them a few times on performance cars the had no cats. It's been while but I'm sure they are still around.

Sent from my LM-G710 using Tapatalk
 

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Discussion Starter #51
Final Data: Today I took my Subie to the local Subaru Service Dept and had their chief tech run their scan. Attached is what he measured. I was told that both front cats are bad and that such is shown by the lack of a delay in the graph on the O2 sensor immediately behind the front cats responding to a change in the upstream MAF sensor, on both sides. This is all he logged. So, do you techies agree with this diagnosis? I don't have anywhere else to turn. Thanks. LRV
 

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I was told that both front cats are bad and that such is shown by the lack of a delay in the graph on the O2 sensor immediately behind the front cats responding to a change in the upstream MAF sensor, on both sides.
It's been my understanding that when a fuel cut is initiated while the car is cruising (which is apparent in the graphs), the pre-cat A/F sensor signal (Lambda) should usually reach full lean (1.4) very slightly before the Rear O2 sensor reaches zero. If the A/F sensor signal reaches full lean well after the Rear O2, the A/F sensor might be defective. However, I've never seen reference to both changing at the same time meaning the cats are bad.

That said, a close look at the A/F Sensor and Front O2 Sensor graphs appears to show the A/F Sensors reaching full lean somewhat ahead of the Front O2 Sensors. Unfortunately, the vertical scale for the Front O2 Sensors, and the horizontal time scale, don't allow a more precise comparison.

Granted, the technician might have past experience where a lack of a delay in the sensor signals was associated with a bad cat. Perhaps others have had similar experiences and can confirm this meaning of the sensor data.
 

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Discussion Starter #53
Thanks Plain OM. Any chance that cardoc is still around? I'd love to get his input on this. The dealer says the two bank 1 and 2 upstream cats are bad, but that the third downstream cat is OK (at least for now). The dealer quotes $5724.26 total price to replace the two upstream cats! Does not include replacing any of the 5 O2 sensors. Outrageous. I'll do some looking around for comparison quotes. But it raises the question of what to do. If the cats are bad, and it won't pass smog, I can't sell it "as is" to anyone except to the State of CA who apparently will give me (and anyone else who wants to get rid of an old car) $1000. That would mean having to buy a new car. This 2005 model has had its problems, but it works well for me as my travel and fishing vehicle. The Gen 4 and 5 Outbacks are bigger and so not as attractive for my size and uses. And, they cost a lot more money. So, perhaps I'll look at another Gen 3 but a '06 - '09 model. But before deciding what to do, I would love to have someone who can really decipher the BlueDriver data I've posted above in several posts and contrast it to the dealer generated data posted immediately above which supposedly shows for certain that the two cats are bad. One last plea for help. Thanks. LRV
 

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Thanks Plain OM. Any chance that cardoc is still around? I'd love to get his input on this. The dealer says the two bank 1 and 2 upstream cats are bad, but that the third downstream cat is OK (at least for now). The dealer quotes $5724.26 total price to replace the two upstream cats! Does not include replacing any of the 5 O2 sensors. Outrageous. I'll do some looking around for comparison quotes. But it raises the question of what to do. If the cats are bad, and it won't pass smog, I can't sell it "as is" to anyone except to the State of CA who apparently will give me (and anyone else who wants to get rid of an old car) $1000. That would mean having to buy a new car. This 2005 model has had its problems, but it works well for me as my travel and fishing vehicle. The Gen 4 and 5 Outbacks are bigger and so not as attractive for my size and uses. And, they cost a lot more money. So, perhaps I'll look at another Gen 3 but a '06 - '09 model. But before deciding what to do, I would love to have someone who can really decipher the BlueDriver data I've posted above in several posts and contrast it to the dealer generated data posted immediately above which supposedly shows for certain that the two cats are bad. One last plea for help. Thanks. LRV
If you do want to put new cats in, the cheapest route would be either have an exhaust shop weld some new ones in, or get a walker replacement exhaust assembly. Dealer cats are expensive. A cut would probably run $60-$150 at a exhaust shop, and another $60-$100 to weld one in. At least this is prices around my area.
 

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$5000 is insane. I believe that Magnaflow might make a full replacement for the 05 that runs a little over $1000.


Magnaflow says "This does not fit your 2005 outback" then at the bottom it says these are for a 2005 outback, so its a little confusing.

I just realized you live in California... that is going to put you in a difficult spot because there are many parts you can't even ship to California including the above.

Does your car actually fail emissions tests? Or they won't even look at it because of the code?
 

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Discussion Starter #58
WantAnOutback: Thanks for the info. I'm informed that in CA the smog tests these days only look at the codes. That is part of my frustration because one shop did have an old style exhaust analyzer and while it showed the PO420 code, the exhaust gases showed they were fine. I have a cheaper quote from a muffler shop than the dealer to replace the front two cats or all three, but now am wondering if it wouldn't be better jsut to buy a "new" used Outback ('06 - '09 model) with about the same mileage as mine which are listed between $5K and $6K, and then turn my poor Subie into the state under the "Cash for Clunkers" program which would give me $1000 for it. But, then, if the cats were original on the "new" car, I might just be heading towards the same PO420 problem in a short time. At least I have a BlueDriver to run the codes on it before buying. LRV
 

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I bought an 07 OB 4EAT in April of last year. 152K. It ran fine all Summer, then that Fall, I lost the original gas cap. After that, constant CEL errors with the new cap. So, I had it checked at a local shop, and was told it was the PO420 code. They recommended that both O2 sensors be changed, and the Cat. I said OK, but never had it done. I kept driving the car, since it ran fine. Well, that Winter, I had the oil changed at Jiffy Lube, (since I couldn't do it outside myself), and while there, I had them do their injection clean (on special). No CEL errors since...
 
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