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2006 Outback 2.5
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Discussion Starter #1
2006 Outback Wagon (MT)
I have been pouring through the many threads that cover catalytic converter codes and other issues surrounding them. Long story but it has been determined by mechanic the car needs a CC. I am tempted to do the O2 sensor or sensor's myself first figuring they will probably need to be replaced anyway even if the CC does indeed need to be done and have a few questions for some of you wiser and more experienced guru's.
1. How exactly do you test each of the O2 sensors, front and back (before and after cat) to see if they are working?
2 Am I understanding correctly that I should start with the rear and then try the front if replacing the rear doesn't do the trick?
3. If it comes to replacing the Cat after all I found Subaru OEM on a site mentioned here (one of the many threads I have read through) and based on the prices and quote I got from shop, they say it should be Subaru OEM...well I'l go with getting my own thank you. I keep seeing front and back Cat's mentioned here however and am confused. Are there 2 CC on this car and if so how do I know which one to replace first? Do you automatically replace both and if so when buying parts do they always come together? I didn't see an indication on the parts site and I can't find a diagram anywhere of the Cat, sensors and any other parts in the system. That reminds me
1.5/3.5 Where are the front and rear sensor in relation to the Cat? Is there a diagram anywhere that might help me get my bearings? There are threads I can probably figure this out with but a diagram would help me understand a lot.

Thanks in advance to you all.
 

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miles you got? any rust where you live?


if just p0420, start by replacing the rear sensor with a denso branded one, ...maybe half the price of OEM, and Densos are known to work with subarus. (whereas bosch gives more problems).
($52 was what rock auto wanted for a Denso when I last looked today for a car similar to yours).

_____

if you got more codes what are they?

edit: any holes or rust in the exhaust up front near or before the cat. (flanges, gaskets, rust, smash holes?)

________

I would not consider buying a cat. I would consider taking off the existing one and having it cleaned. (like with bottles of treatments that remove the contaminants. )

if the thing when taken off is all busted inside,...I would consider buying a cat.
 

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2008 Outback 2.5i
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Front sensor is an AF ratio sensor. It is on the exhaust pipe right before the first cat. It is located below the black air intake part at the front of the passenger side of the engine compartment that carries intake air from the front to the air cleaner box.

When you can see the front sensor you should be able to see the rear one. It is closer to the inside of the front passenger fender, near the bottom, of course. It is downstream of the cat and accessible from the same spot where you access the front sensor. Their electrical plugs are located next to each other near the front passenger corner of the engine.

The front cat itself is mere inches below the boot on your passenger side CV axle. The heat from the cat is why those boots fail so often. Thanks subieenginers!
 

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I've replaced a GEN3 front cat with aftermarket. You basically get a whole new exhaust manifold/pipes/front cat. The main issue -- if it's an issue for you -- is that the exhaust heat shields may not fit with some of the aftermarket units. Otherwise, works fine.

Sensor and front exhaust replacements are pretty easy jobs.
 

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1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
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This photo of a catalytic converter for at 2006 OBW 2.5 from Rock Auto shows the front and rear sensor bungs (note photos used to show O2 sensor locations, not a recommendation of what or where to buy).



The rear Cat doesn't seem to have a place for a sensor

 

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1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
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As far as testing the O2 sensors I believe the best way is to compare live data while running to check sensor voltages. That can also help determine cat effectiveness. I know that in the older (up to 04) you should check the front and rear cats with an IR Thermometer to verify there was at least a 100 degree change between the front and rear, but I don't know if this is a valid test for your car. User Cardoc has a large P0420 thread that has some good info on how to check.

http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diagnosis.html
 

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2005 Outback R LL Bean 3.0 H6 w/ 5 speed sport shift
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So, this probably won't go down good with some on here because of the sponsorship. I will speak from personal experience and you can make your own decisions.

I purchased two different sets of cats from a manufacturer shown above and even though my air fuel mixture and no oil loading of the ceramic element, both sets on my H6 went bad. So much so that when I removed them from the car and tipped them up and down I could hear and actually see the ceramic sliding around inside, which was making a terrible rattling noise. Additonally, when I looked into the o2 port, I could see the "flat" end had become cone shaped and I suspect it was restricting the exhaust flow and caused some burnt valves on a different engine.

The company was very agreeable though and refunded the entire amount of the purchase. I didn't even go into the burnt valves because I knew what a PITA that would be.
Finally, I ended up purchasing Magnaflow. They fit perfectly, they have the heat shields already in place and I've had them on for several months with no signs of failure.

But let's back up a bit:

I had taken my car to a muffler shop right after purchasing it because I had a bad rattle. The owner said I had a bad cat on one side and it needed replaced but he didn't have the type I needed in stock. Long story shortened, after all the dealings with the other cats, I decided to cut the originals open to have a look....perfect inside!

Moral: Don't believe anything you don't see with your own eyes!
 

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1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
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I do believe that the consensus among experienced Subaru independant shops is to use only Subaru OEM catalytic converters. Many say that the aftermarket ones are junk and don't last. Again, you get what you pay for. Definately like real world experience to help make a decision. Like most say, the cat would be the last item to suspect.
 

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2006 Outback 2.5
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Discussion Starter #9
miles you got? any rust where you live?

Thanks Eagleeye,
190,000 heads were done maybe 20,000 ago. Yes rust where we are but the car spent a good portion of it's life out west and doesn't have a rust problem.


if just p0420, start by replacing the rear sensor with a denso branded one, ...maybe half the price of OEM, and Densos are known to work with subarus. (whereas bosch gives more problems).
($52 was what rock auto wanted for a Denso when I last looked today for a car similar to yours).

It has other codes as well, unfortunately I can't find the sheet they gave us with the codes they found but even they said many were old. I know one of the codes is for front wheel speed sensor which has already been replaced and there is either a SRS code and or light that has been around. Shop that spent some time checking codes said something about the codes and readings before and after Cat leading them to believe it needs replacing. I know one of those codes at least has been the p0420 and I think there was at least one other pcode as well.
From what I gather based on threads replacing that downstream (after the Cat) sensor with aftermarket is fine so I will go with that Desco you mention but the upstream (before Cat) should be Subaru OEM, right?

_____

if you got more codes what are they?

edit: any holes or rust in the exhaust up front near or before the cat. (flanges, gaskets, rust, smash holes?)

See above, I will look for that sheet again. No no rust in the exhaust or major rust under the car.

________

I would not consider buying a cat. I would consider taking off the existing one and having it cleaned. (like with bottles of treatments that remove the contaminants. )

if the thing when taken off is all busted inside,...I would consider buying a cat.
I don't remember anyone talk abut taking it off to clean, that's interesting. The shop actually suggested we try running a particular type of cleaning stuff through or pay them $100 to do a cleaning of some sort and we did put some of the additive in to run through I think it was 1/4 tank (?) after which there was some improvement but not for long. The car hasn't always run this poorly even with throwing the codes but now it has no power particularly at lower speeds RPM's I would say. Feels like it isn't going to make it up some hills.
 

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I don't remember anyone talk abut taking it off to clean, that's interesting. The shop actually suggested we try running a particular type of cleaning stuff through or pay them $100 to do a cleaning of some sort and we did put some of the additive in to run through I think it was 1/4 tank (?) after which there was some improvement but not for long. The car hasn't always run this poorly even with throwing the codes but now it has no power particularly at lower speeds RPM's I would say. Feels like it isn't going to make it up some hills.
what are the codes?

they really can tell why stumbling and near stalls are happening.


try getting them with this which may give better or different then any hand held, (the onboard one might take a couple tries for you to get your timing right for it to tell its tale).




http://www.subaruoutback.org/forums/109-gen-3-2005-2009/19053-05-06-09-how-read-diagnostic-trouble-codes-dtcs.html
 

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Discussion Starter #11
Front sensor is an AF ratio sensor. It is on the exhaust pipe right before the first cat. It is located below the black air intake part at the front of the passenger side of the engine compartment that carries intake air from the front to the air cleaner box.

When you can see the front sensor you should be able to see the rear one. It is closer to the inside of the front passenger fender, near the bottom, of course. It is downstream of the cat and accessible from the same spot where you access the front sensor. Their electrical plugs are located next to each other near the front passenger corner of the engine.

The front cat itself is mere inches below the boot on your passenger side CV axle. The heat from the cat is why those boots fail so often. Thanks subieenginers!

This is a great description, thank you! This may make you roll your eyes and I know I have read about it in these threads but are you accessing them from the top, the engine under the hood or from underneath the car? RA also suggest a tool to help replace the sensor, is that necessary or even helpful? Worth it?

How long ago did you replace yours? From many accounts and based on what the shops have said aftermarket cat's just don't last and it's worth the extra to use Subaru OEM. Not sure if the OEM comes with the heat shields or not, I will look but I also remember reading that those shields can create problems so making sure it all fits is a good reminder to check it all, thanks.
 

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Discussion Starter #12
This photo of a catalytic converter for at 2006 OBW 2.5 from Rock Auto shows the front and rear sensor bungs (note photos used to show O2 sensor locations, not a recommendation of what or where to buy).



The rear Cat doesn't seem to have a place for a sensor


So the car does have 2 catalytic converter's then. How does one know which Cat needs to be replaced? Since the sensors only seem to work with the front one (one in the first picture) does that mean that's the one everybody is referring to when talking about codes and replacing or do people replace both automatically when doing a Cat? If the sensors only sense info from the first one that means replacing just that one should solve any codes that are indeed a result of the CC, right?

By the way, these are just the kind of photo's I have been looking for. Thank you! It would be nice to have one of those drawings that label all the parts as they go together too but these photo's help a lot and combined with Mr. Toad's description of how to find the sensors, even I should be able to figure that out! Hehehe Thanks to you both.:grin2:
 

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Discussion Starter #13
As far as testing the O2 sensors I believe the best way is to compare live data while running to check sensor voltages. That can also help determine cat effectiveness. I know that in the older (up to 04) you should check the front and rear cats with an IR Thermometer to verify there was at least a 100 degree change between the front and rear, but I don't know if this is a valid test for your car. User Cardoc has a large P0420 thread that has some good info on how to check.

http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diagnosis.html
I have read through that thread in the past, thank you. I don't remember seeing a clear method for testing just the sensor but it may be more about me not fully understanding what was being said and or not having the same code reading equipment. I haven't invested in the reader that allows the use of the program that you can tune with too (I'm forgetting the names at the moment but I do have them). I did get a cord that allows me to use OBDwiz and I have that on my laptop but I'm not very experienced with it. I just got it a week or so ago when we couldn't find the codes the shop had given us because I didn't feel the need to pay them again to do that and figured it made sense to get something I can use on all our cars. I probably should have gotten one of the hand held's but thought I was understanding that this would give me more than just the basic generic codes and read some manufacturer/model specific like SRS and ABS codes. I remember seeing something about using a heat sensor on some cars but first I would need an IR thermometer for one and I don't remember it being mentioned for Gen 3 either. I'll look at that thread you mentioned again though, maybe I will absorb it all better this time...it is a long thread as I recall but the original post in particular has some great in depth info on it's own. Thanks!
 

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For the Catalyst:

Testing for temperature-differential is a good INDICATOR... but not necessarily a definitive test.


Using scan-tool, monitor both O2 sensors.
*) Front should be jumping up/down in closed-loop operation as the computer constantly adjusts the injectors.
*) Rear should nearly ALWAYS remain HIGH even when you open the throttle a bit.

Finally: Do a richness test by feeding propane into the intake manifold while monitoring O2 sensors:

*) FRONT should settle out. (stop pulsing) because you are shoving the propane into the engine and the computer responds by shutting down fuel-injectors.
*) REAR should STILL remain HIGH which indicates that the catalyst is effectively burning off the excess hydrocarbons coming out of the engine.

BOTTOM LINE: If the rear O2 sensor does not nearly ALWAYS REMAIN HIGH. Either your catalyst or the sensor itself is at fault. (I assume you know that exhaust leaks must not exist lest the system gets out of balance.)


EXAMPLE ==>
 

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I linked the onboard diagnostics link for 2005-2009 cars before,

wondering if there was some other codes denoting a front o2 sensor, or any other code.

the OP could use the same to read airbag, abs, etc. without any handheld anything that may or may not like subarus.
(I wish all the cars had such a thing)

I have no plans to drive to vermont,...ask for the key, and follow the directions in the thread on this car though. :wink2:
 

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Discussion Starter #16
what are the codes?

they really can tell why stumbling and near stalls are happening.


try getting them with this which may give better or different then any hand held, (the onboard one might take a couple tries for you to get your timing right for it to tell its tale).




http://www.subaruoutback.org/forums/109-gen-3-2005-2009/19053-05-06-09-how-read-diagnostic-trouble-codes-dtcs.html
I tried reading them from the car back when we first got it and for some reason wasn't successful in getting it to work very well. But it's been quite a while since I tried that, maybe I should give it another shot. Thanks, I will try it again later or tomorrow, I think I will try using the computer program while driving too when I have someone to drive so I can just focus on the computer and see what info I get that way too. Thanks
 
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