[matt88-8]

Hi all! Ive collecred some data and am hoping someone can help me figure out my next step.
Back story:
I have a 2007 outback. 2.5i. 200,000km.
A few weeks ago, the coil burnt out and I lost cylinder 3&4. I drove about 5km home hoping to avoid a late night tow bill. Long story short new coil and the car runs great, but now I have this code p0420. . The car smelled pretty bad of fuel while it was missing, but I don't wanna drop a grand on a cat if it survived...

I got this data off my phone running the torque app. I also have a video from the snap on scanner. I'm working on uploading it.

I don't know how to interprete the data I'm getting, but the downstream sensor looks good. I know cats are pretty robust critters but have heard these ones are prone to rust off/out

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[eagleeye]

this is regular stuff here, daily / weekly p0420 crap. ...that code by itself is minor,...

last thing you do is replace a expensive cat, (although that is typically the first thing on the list for a dealer,...as long as they can stick the cost on someone)


as far as that many kms. = 124,000 miles.

on my own 2.5 car I have replaced the rear o2 sensor twice with denso branded ones. (once at 65,000 miles, and again around 95,000).
@plain OM has a car just like yours though, and maybe able to make another suggestion looking at your data.

_______

 

[idosubaru]

That 9.4 long term fuel trim looks a little high to me, but I'm not well versed in them so maybe that's normal under some conditions.

Since the car was just worked on - I would look for vacuum leaks.

Were any intake hoses or PCV hoses removed, touched, or moved during the previous repair? That would be the obvious starting point.

 

[plain OM]

Those screen shots are hard to draw much from.

Of the six, it appears that in at least four, the rear O2 (B1S2) voltage is quite unstable. That is a possible sign of a bad cat.

With a warmed up system, and either idling steadily or driving at a steady speed with little if any throttle variation, the rear O2 is normally fairly stable in my experience, and I'm monitoring real time. (In that I mean the variations are not often more that one or two tenths.) But what I'm seeing in several graphs is regular oscillations going from 0.7 to 0.2 or 0.3 V and back up. An oscillating rear O2 signal could be a sign of a bad cat.

However, from the graphs we can't tell the time frame -- the horizontal scale isn't identifed. This could be relevant to the rate of the oscillations. Also, we can't tell if the B1S1 voltage is varying at the same time or is relatively steady -- the vertical scale is too large.

The criteria for the P0420 is based on statistical analysis and comparison of the variations in the signals from the front and rear sensors, i.e., B1S1 and B1S2. There are many factor taken into account by the OBD when running its cat efficiency test, but a (my) highly simplifed interpretation of the underlying logic of the test method is that if the front sensor is stable while the rear sensor is oscillating, then the cat isn't functioning properly.

The data we could have might verify what the OBD is seeing, and we can look for anomalies that could be contributing factors.

I don't know if the Snap-On scanner video might have more information. As a read of http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diagnosis.html and http://www.subaruoutback.org/forums...spective-p0420-catalytic-efficiency-code.html would reveal, even with a fuller list of parameters, it's often difficult to conclusively determine that the cat is bad.

@eagleeye -- The subject of this thread should be "P0420 data interpretation". It's an encompassing title and so I've attached the 2007 FSM pages for P0420 Detecting Criteria and P0420 Diagnostic Procedure, both of which make reference to the rear O2 sensor signal stability. I think that with an understanding of the methodology used by the OBD in regard to P0420, we might be better equipped to diagnose a possible bad cat and its cause.

That said, driving with misfires in two cylinders, and raw fuel being exhausted into the cat, could well have caused the cat to overheat.

 

[plain OM]

That 9.4 long term fuel trim looks a little high to me, but I'm not well versed in them so maybe that's normal under some conditions. . . ..

I was looking at the LTFTs in relation to the MAF as well. There seems to be a relationship, but the MAF scale is too large. On my 07 the LTFT does go up according to increasing MAF ranges, and it's something I've been trying to verify for some time. (See, for example, the chart in this post. )

 

[matt88-8]

Thanks for the replies guys. The code for the cat came up before I worked on the car, but I have checked it trying to find a leak. I know the scale of the torque app is poor at best, but I can't seem to get the video to upload. Not sure why yet.

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[eagleeye]

Thanks for the replies guys. The code for the cat came up before I worked on the car, but I have checked it trying to find a leak. I know the scale of the torque app is poor at best, but I can't seem to get the video to upload. Not sure why yet.

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probably need 10 posts.

@plain OM this thread has that title now,...??
and I wonder if you are going to suggest the code be cleared,...and see if it reappears. ...torque pro clears codes really nice (no hard or easy restart).

 

[matt88-8]

I've cleared it like ten times

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[matt88-8]

Datahttps://cloud.tapatalk.com/s/599ed9c0031ba/20170818_181443_002.mp4

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[plain OM]

. . . @plain OM this thread has that title now,...??
and I wonder if you are going to suggest the code be cleared,...and see if it reappears. ...torque pro clears codes really nice (no hard or easy restart).

The current title is " P4020 data interpretation" (Link to current address: http://www.subaruoutback.org/forums...46-p4020-data-interpretation.html#post5014394 )

I raised the concern because that won't get caught by Title searches for P0420.

 

[eagleeye]

Datahttps://cloud.tapatalk.com/s/599ed9c0031ba/20170818_181443_002.mp4

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can you upload that to youtube and post some semblance of the link without the http://youtube on the front?,...I will correct the link so it will post.

 

[matt88-8]

Didn't seem to work the first time around.https://cloud.tapatalk.com/s/599edb1f1b440/20170818_181443_002.mp4

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[plain OM]

Thanks for the replies guys. The code for the cat came up before I worked on the car, . . .

Do you mean the P0420 appeared before the coil failed? If so, how long before -- are we talking just a few days, or several weeks and many kms? (I.e., could the two still be related?)

I looked at the video, but for me it has many of the limitations of the screen shots. The rear O2 voltage is varying, while the front A/F sensor voltage, for the most part, appear stable. We can't see what other engine operating parameters are indicating. It's different if the scanner is right with you and the screen can be scrolled to look at related data at the same time (e.g., MAF, rpm, STFT, throttle position, vehicle speed, etc.)

[I'm far more familiar with Romraider, which is a free Subaru-specific program that accesses the (proprietary) Subaru SSM data stream, and provides a more comprehensive list of parameters. In the P0420 Diagnosis thread, many, if not most, of the discussions make use of Romraider, to various degrees because of its familiarity, larger list of available data, and recording capability. The latter is especially useful as it facilitates sharing of real-time logged data in a spreadsheet format. When attached to a post, that allows others to select and analyze different parameters, which is far easier than looking at multiple screen shots, or a "moving" video of a display screen. Romraider uses a Windows or Linux computer (laptop) and, if the objective is only to monitor and record using the "Logger" tool, then it requires only a relatively inexpensive OBD-USB adapter cable (Vag-Com KKL 409.1). (Romraider can also used for tuning but that requires a different, and more expensive adapter.) It might be something to consider. http://www.romraider.com/]

 

[eagleeye]

The current title is " P4020 data interpretation" (Link to current address: http://www.subaruoutback.org/forums...46-p4020-data-interpretation.html#post5014394 )

I raised the concern because that won't get caught by Title searches for P0420.

fixed title.

 

[matt88-8]

Before I worked on the car but after the miss happened. Rom raider sounds cool, will look into that.

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[matt88-8]

Thanks guys for the help so far, i do appreciate it.

The snap on scanner will provide tons of data, in both the graph view and in the numerical view. If you make a list of what would be helpful I can make the graphs reflect that. (romraider adapter is like $165 american)
I can shoot a better video with whatever data you guys can make use out of. It also has a data logger function i can try out.

the first post about this being a daily occurrence on this fourm has me a bit worried, This is my first subaru and so far i have a caster pull the dealer cant fix, a burnt out coil and now a emission issue, all in the first three months of ownership. Are these vehicles high maintenance? or am i just unlucky?

 

[eagleeye]

Thanks guys for the help so far, i do appreciate it.

The snap on scanner will provide tons of data, in both the graph view and in the numerical view. If you make a list of what would be helpful I can make the graphs reflect that. (romraider adapter is like $165 american)
I can shoot a better video with whatever data you guys can make use out of. It also has a data logger function i can try out.

who said that? I use a $10 VAG cable.

tactrix $165 stuff is only for people flashing / reflashing so they don't "brick" the ECU while reloading,

but you are just passively reading it.

(so $10 VAG cable, free rom-raider, a working windows laptop that you already hopefully have, = $10 total.

 

[matt88-8]

does romraider have a bluetooth interface that would work with me current obdII adapter?

Or what VAG-COM cable? something with 409.1? anything specific?

 

[plain OM]

does romraider have a bluetooth interface that would work with me current obdII adapter?

If your laptop has BT, Romraider can work through it. (I use RR on a BT-capable laptop that has had Win8 and now has Win10.) But you also need an adapter (the plug-in device at the OBD connector) that can access the Subaru "ssm" data (aka "k-line"), which is not the same as the generic OBD data that many generic adapters and display tools such as Torque, work with.

What adapter do you have? It's specifications might help determine what it can do.

Or what VAG-COM cable? something with 409.1? anything specific?

Vag-Com KKL 409.1

See this post, and that thread for more info.

 

[matt88-8]

Finally got some time and some shop space to do a visual inspection of the exhaust. Found this. The plastic (wind deflector?) Is melted under the cat. Pretty cool looking, but definitely new since last time I was under the vehicle...

The exhaust isn't blue or anything strange but the plastic is definitely melted away from the exhaust (down) the angle for pictures was less than ideal.

If I do end up replacing the cat should I do the front cat only as its the only one being monitored by the ecu? Or Bite the bullet and do both?

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