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Discussion Starter #1
This is regarding my 2005 outback H6 LLBEAN (california emissions) - I live in PA..............

Going to replace both left and right sideCats, I am using the "right" side as a example of difference in "ID" numbers and price

I have always used Subaru parts for replacement so that I avoid any headaches with aftermarket....but this is odd:
So Subaru has two part numbers for their catalytic converter & front pipe:
-44105AG37A ID:FCAG8 : $1344.00
-44620AA37A ID:FCAM6 : $857.00

I am guessing that the difference is only that the FCAG8 means that it is approved for Cali use and is more restrictive. (double honeycomb?) and that the FCAM6 is less restricitve and single honeycomb, thus the price difference. I assume which ever one I choose it will fix the code, since the car only looks for response on the rear sensor in comparison to the front.

So can anyone confirm my suspicion regarding the meaning of the "ID" diferences and has anyone had success with installing the 49 state on their Cali car.

My car has 160,000 miles on it and is in mint shape. I just want my mileage back and no more code. "PO 420 Bank 1 below threshold"
Ive checked live data on OBD2 and it appears the sensors are working as they should. there is no dead voltage, only extreme voltage fluctuation on the rear sensors when flooring it.

thanks in advance for any input!!

Dave
 

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All the H6s were Cali. There are 3 cats in the y-pipe assembly. The y-pipe is in two pieces. Bank 2 has two cats, bank one a single cat. 37A is the left pipe, 36A is the right. The RIGHT side is bank 1. The part number you listed is bank 2. The ID numbers don't reference the substrate type. Think serial number.

You can use aftermarket cats. You can even visit your favorite exhaust shop and have them weld in a single, or change both. What did the data off bank 2 show?

Since you said the waveform is sporadic instead if steady, it's definitely toast. I suggest you find what killed it and repair it so the new one or the other one doesn't dive on you. Also, if the problem is severe enough, you may get a P420 right off the bat.
 

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Discussion Starter #3 (Edited)
Thanks Cardoc, I appreciate it, yep thats what I understood as well, the 37a designates bank 1 but there are two different part numbers for the bank 1 options. Here is a link to the dealer I was looking at, there are two left bank options listed about half way down EXHAUST. FRONT PIPE.. 2005 Subaru Outback 3.0L 5AT L.L.Bean | Subaru Part Wholesale, Libertyville Illinois

what do you think about the price difference?

Also car seems fine, drives fine, fuel efficiency is down - around town winter I get around 16-17 MPG. plugs have been replaced with NGK, replaced valve cover gasket on passenger side, new pcv valve, no signs of head gasket leak, car has been garaged its whole life. temp gauge is always right in the middle, has climbed to 3/4 mark when towing camping trailer up a big hill in the summer. Never any other code.

Here is a link to the live data on youtube... if you dont mind, could you give me your opinion , sorry the video is not the best...

Thanks
 

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hold up, have you properly data logged the car to confirm it is not a failed rear o2 sensor? I just got done replacing my rear o2 sensors on my 2010 Outback 3.6R for the same reason....sensor was going bonkers on bank 2 (passenger side rear sensor).

That is too expensive of a repair to shoot ye old parts cannon at it...

If your cat failed your rear o2 sensors in most cases will follow the primary ones alternating between rich and lean...
 

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Okay, one more time.

BANK 1 is the right side of the car.
BANK 2 is the left side if the car.

P0420 is for bank 1
P0430 is for bank 2

Since you have 4 sensors, 2 are behind the cats, P0420 is referring to bank 1, right side.

You can use a fed cat and it will be fine.
 

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Discussion Starter #6
Cardoc, thanks! I did not know PO430 is for bank 2. I just thought the 420 was for any cat issues. Im gonna try the Fed Cat and go from there. One more question. Should I replace the sensor as well? or as YeuEmMaiMai recomnded try the sensor first? I do smell some sulfur at times, so I am guessing it really is the Cat. Also, why is so common for the Bank 1 cat to go in these H6 cars? seems odd to me. Thanks again, coming from a guy who knows enough to get into trouble. :)

Dave
 

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Discussion Starter #8
when you say you smell sulfur at times, is it when the car is cold? is the car running excessively rich?
Usually when the car is warm and giving it gas to stay with traffic during drive periods of 15 to 30 minutes. Doesnt usually smell when cold or for short around town drives.Thanks YeuEm.
 

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Your Cali car has 4 sensors that control fueling for each bank and monitor each cat independently. P0430 may not have popped up because that bank hasn't deteriorated yet, or the ECM is monitoring it.

When you look at the data available, do you see O2 sensor 1/2 and 2/2, or O2 sensor bank 1 and bank 2? The main thing is can you see data from both rear sensors? Do they both have an irregular waveform?

As for a bank 1 cat going bad first, I can only say that bank 1 is the hot side of the engine. I've not noticed any particular pattern of failure for either bank. Earlier models with the H6 only had 3 sensor and the rear sensor is mounted behind the 3rd cat after the Y connection and when it throws the P0420 it could be either or both front cats causing it.
 

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Discussion Starter #10
Your Cali car has 4 sensors that control fueling for each bank and monitor each cat independently. P0430 may not have popped up because that bank hasn't deteriorated yet, or the ECM is monitoring it.

When you look at the data available, do you see O2 sensor 1/2 and 2/2, or O2 sensor bank 1 and bank 2? The main thing is can you see data from both rear sensors? Do they both have an irregular waveform?

As for a bank 1 cat going bad first, I can only say that bank 1 is the hot side of the engine. I've not noticed any particular pattern of failure for either bank. Earlier models with the H6 only had 3 sensor and the rear sensor is mounted behind the 3rd cat after the Y connection and when it throws the P0420 it could be either or both front cats causing it.
Your Cali car has 4 sensors that control fueling for each bank and monitor each cat independently. P0430 may not have popped up because that bank hasn't deteriorated yet, or the ECM is monitoring it.

When you look at the data available, do you see O2 sensor 1/2 and 2/2, or O2 sensor bank 1 and bank 2? The main thing is can you see data from both rear sensors? Do they both have an irregular waveform?

As for a bank 1 cat going bad first, I can only say that bank 1 is the hot side of the engine. I've not noticed any particular pattern of failure for either bank. Earlier models with the H6 only had 3 sensor and the rear sensor is mounted behind the 3rd cat after the Y connection and when it throws the P0420 it could be either or both front cats causing it.
Thanks Cardoc. Appreciate the info. Im going to start with both rear sensors. I was watching live data waveforms and they both were all over the place and then would go flat for a period then erratic again. Maybe I'll get lucky. I had sniffed aroudn with some propane in the fall looking for a vacum leak around the intake mainfold, but maybe I'll do that again to be sure I eliminated that possibility. Im going to get the NTK's off Rock Auto unless anyone tells me otherwise.
 

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Discussion Starter #13
Those or Denso. As long as it's not a Bosch. They can't keep up.
So upset at myself.... scratched a sensor shield trying to get one in...i assume its now no good? Looks like it has some kind of coating on it that i assume should not be disturbed? Holding off on installing it until i hear feedback.

Thanks. Dave
 

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So upset at myself.... scratched a sensor shield trying to get one in...i assume its now no good? Looks like it has some kind of coating on it that i assume should not be disturbed? Holding off on installing it until i hear feedback.

Thanks. Dave
 

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Discussion Starter #16
I did, seems to work. The voltage on the code reader is still up and down, but not all over the place like it was. The wave lengths are longer as well. I cleared the codes, it usually comes back after a half a tank to full tank so well see if it comes back. Thanks.
 

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Discussion Starter #17
have about 75 miles since the sensors installed. The live data shows some fluxuation but not as jumpy or erratic as it was. here is a vid of the live data while driving. Sorry bout the quality..... Any input as to whether the fuel trim is normal and the voltage on downstream sensors would be appreciated. If the light comes back on, should I replace the A/F sensors as well? They are original to the car with 167,000 miles on it. If that does not do it, I assume the CATS are just worn out. From what I understand it is recomended to replace the sensors if you replace the cats on a car with that many miles on it?

Link to vid:
 

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Discussion Starter #18
Light came on. I guess I'm gonna throw some OEM Cats in there. Should I replace the A/F at the same time?
 
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