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2010 outback
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26 Posts
Discussion Starter #1
I have an 05 Outback 2.5 and this P 420 code just poped up. My mechanic tole me that it is a cataylic converter deficiency. How long does Subaru warranty the catyalic converter? Is this a pricey item? Can I drive the car as is?
 

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2005 3.0 R n totaled
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EPA (Federal Government Agency) regulates warranty of emission components as follows:

Emission control and emission related parts are covered for the
first 2 years or 24,000 miles of vehicle use; and

* Specified major emission control components are covered for the
first 8 years or 80,000 miles of vehicle use.

I would suspect that if it is catalytic converter itself, that would be considered as "major" component.... I am not sure about that though... it depends, who is diagnosing the problem. I suggest to go to authorized Subaru dealer/service station.
 

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2010 outback
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26 Posts
Discussion Starter #3
P 420 Code

I forgot to mention that the car has 91,000 miles and is 7 1/2 years old
 

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Car: 2008 Tribeca, 2010 LGT, Sold: 2005 XT Limited
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It's unlikely to actually be the catalytic converter. Search P0420. Pay attention to cardoc's posts.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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2008 OB2.5i LTD
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My front catalytic was replaced at 120k after it was verified with a computer monitored test drive by the mechanic. Ironically P0420 came up on the way to the dealership for a 30k service
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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My front catalytic was replaced at 120k after it was verified with a computer monitored test drive by the mechanic. Ironically P0420 came up on the way to the dealership for a 30k service
How many miles since the CAT was replaced? It could be the original problem is still there or another popped up.

There has been only one Subaru that I have had to install a third CAT on. The first was done under warranty at 70k, the second at 150k. The second CAT was from Subaru, they installed it. I put the third in, from Subaru because its all one assembly. The only thing I could estimate for the short lifespan was the type of gasoline the owner was using. Low grade. I could not find any issue with anything. It was an 08 Impreza. The owner has since stopped using the "cheap" gas.

The CATS are designed to last a long time with proper maintenance and fuels. I am at 211k miles on the OE CAT on my 96 Cavalier.
 

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2010 outback
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26 Posts
Discussion Starter #9
P 420 Code

Another thing I forgot to mention was that the plugs and wires were just changed as part of a 90,000 mile service, along with changing the power steering, brake and transmission fluids. I found it very interesting that a few days after the service the code popped up. Could something here be the cause of the code?
 

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OBW H6 VDC, Tribeca, XT6
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12,385 Posts
the P0420 code is a debacle. you can google it or search the plethora of online forums about it, it's unbelievable common and a bogus issue.

a $5 02 extender off ebay solves it most of the time. that's the best place to start before jumping into this big mess.
 

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2008 Outback 2.5 L.L. Bean
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I have a CEL on as well, and just found out it's a P0420 code. The guy at Auto Zone said it's probably an O2 sensor by the header since it's in Bank 1. Time to shop around and see how much the part costs so I can just fix it myself.
 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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I have a CEL on as well, and just found out it's a P0420 code. The guy at Auto Zone said it's probably an O2 sensor by the header since it's in Bank 1. Time to shop around and see how much the part costs so I can just fix it myself.
Bank 1 is both banks on the 2.5. There is one forward AF sensor and one rear Oxygen sensor.

Don't shop til you know what to shop for.
 

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the P0420 code is a debacle. you can google it or search the plethora of online forums about it, it's unbelievable common and a bogus issue.

a $5 02 extender off ebay solves it most of the time. that's the best place to start before jumping into this big mess.
Do you just "cut & paste" this?

This is the type of advise that gets on my nerves.

GG, would you cover the cost of a major repair if someone takes your advise on a $5 fix and the actual repair ends up causing damages costing 100s or 1000s? If its a stuck thermostat, the end result will be head gaskets or cracked head(s) or radiator. If its fuel related and gets worse, detonation which tends to burn valves or overheat the combustion causing piston damage. These are just two possibles.

Any issue left to fester will domino into a worse state. That state depends on the origin and reactions.
 

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OBW H6 VDC, Tribeca, XT6
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I get your concern, folks should be knowledgeable and not run a car with issues, running lean, rich, etc - that is true of any engine whether it has a rear O2 sensor or not - I'm assuming people are taking proper precautions outside of the code. Ignoring the code one should easily be able to properly own and maintain an engine just like one could before rear O2 sensors ever existed - and Subaru's were just as (or more) reliable. I should qualify more - but the shear volume of 0420 codes makes it tough - really new O2 sensors are probably needed - how many are old, lazy, inaccurate, and need replaced.....so yeah, I see what you mean to an extent and some qualifications are needed.

Before the advent of rear O2 sensors, Subaru engines were not dying in mass numbers at low mileages/ages. If a thermostat sticks, folks should see the temp gauge and not drive the car. If fueling is an issue folks should notice symptoms and address it. Etc. I have no desire to monitor engine condition via a sensor and code that wasn't intended to do that - the rear O2 sensor and P0420 are for emissions, I personally have no need for that sensor or P0420.

I'm glad you're well versed in it, it's nice having both sides available and let people choose.

Converter replacement seems the most common quote/issue/thread post. Those bother me like my suggestions bother you simply because it's a waste of money. Most converters that get replaced pass emissions tests. It's astounding how many are getting replaced when they'd pass an actual sniff test. Owners are getting hosed - thousands of dollars of parts are quoted in mass and that's not good for many owners. So far I'm batting perfect and I've wasted very little time, and no ones money on thousands of dollars of converters - never replaced one (except for rust LOL). Your approach may be better than mine, but mine is better than many of the common converter replacement suggestions IMO. It's certainly been helpful to some and I think there's an enormous amount of people thankful for the easy work around.

Do you just "cut & paste" this?
I should, or create a thread I can link to.

This is the type of advise that gets on my nerves.
But it doesn't cause any issues:
1. rear sensor isn't used for engine control, so it can't do anything. so yes - I will warranty something that can't happen.
2. rear sensor can be completely removed, unplugged and car will run indefinitely with no issues (see #1)
3. older Subaru's never had rear O2 sensors and it caused no adverse catalytic converter failures or engine problems because of lurking engine issues people never knew without the P0420 code. actually it was the opposite - catalytic converter failure was almost unheard of for 1980's and early 90's Subaru's, before there was a code for it.
 

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But it doesn't cause any issues:
1. rear sensor isn't used for engine control, so it can't do anything. so yes - I will warranty something that can't happen.

Not true. Rear O2 sensor data is used to assist in STFT to help control the catalytic converter temperature. The reason a front sensor is switching is to relay a confirmation of what the ECM is doing to maintain a temperature control without overheating the CAT. Switching from lean to rich is a cooling effect. In the old days, air pumps cooled the CAT. When the pump failed, melted CAT. The cars would run with a bad CAT and you wouldn't know it, yes, unless it clogged. With new programming of the ECM and new AF and O2 sensors, data is much quicker, reaction timing is faster, the CAT is cooled more efficient with less parts and efficiency of the engine and CAT performance is seen in many ways, as well as a longer CAT life.

The rear O2 sensor data will also tell you if the engine is running too rich or lean when a known good CAT exist. Knowing how the sensor operates helps to find the real problem.


2. rear sensor can be completely removed, unplugged and car will run indefinitely with no issues (see #1)

Also, not true. It will run with the rear sensor unplugged. It will also run with the AF unplugged. It will run with the IACV unplugged (with some creativity). It will run with the EVAP system disconnected (Although you may want to be careful removing the gas cap). It will run with the ECT unplugged. It will run with the fans unplugged.

But in order for the ECM to operate the engine in a manner that makes it perform and put out the power it was designed for, all these need to be plugged in, operational and in the correct position. Leave that rear O2 unplugged long enough and the programming changes to a lesser output to try to save the CAT. Pull it out of the air stream and the ECM will add fuel to cool the CAT because it will think its getting hot. Given enough time, carbon will begin to clog the combing. All ECMs are programmed to save the CAT while putting out the performance. My VDC is. I want the sensor in the exhaust so if something happens that I don't see from the gauges and extra gauges in the car the ECM will see it and say "Hey, something's up. Find it before it causes damage.". I can't drive around while watching data all the time and I can't record it in 20 minute or hour plus intervals for later review.


3. older Subaru's never had rear O2 sensors and it caused no adverse catalytic converter failures or engine problems because of lurking engine issues people never knew without the P0420 code. actually it was the opposite - catalytic converter failure was almost unheard of for 1980's and early 90's Subaru's, before there was a code for it.

Again, CATs would fail and you wouldn't know it until it clogged up enough. And running and running proper are two different things.

I try to explain things simply. Every sensor on that car has a purpose and some do more than you believe them to. That rear O2 is apparently one of them. We aren't talking about a 1987 GL. It was basic. Nothing has been basic since 1995 Japan markets. These newer cars are programmed for power output increases with lower amounts of engine volume. It is accomplished through computer programming and ignition/fuel mapping that works much faster than your pen and paper trying to calculate fuel density, air density, air temperature, barometric pressure, water/alcohol content ratios, weight of the car, gear and gear ratios, drag, tire size, and throttle opening effectiveness. Its not a carburetor. Remove the data or alter the data the ECM receives and the programming changes. You won't notice it right off. Just like you don't notice a difference between using Wal Mart gas over a major oil company blend. But its there. And it kills. Slow like cancer. Sometimes quick.

Give people a choice. Sure. Here's the choice: Protect the investment that you rely on daily, or, take your chances and roll the dice. I choose the first. Anyone choosing dice, try going without your or any car for 3 days, normal work days, everyone in the family, then think about it again.
 

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Two bottles of 97% isopropyl alcohol (rubbing alcohol) and two bottles of fuel treatment next two times you fuel up. Clears up 90% of the cars that come into our shop. 95% of our cars are Subaru's BTW, the other 5% is Toyota's and whatever crap the boss agrees to work on.
 

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Right on, please keep informing all of us. What I know is that too many converters are being replaced, people are confused (including me admittedly), and like I keep saying it's a debacle.

Replacing converters that pass emissions is pointless to me, particularly for thousands of dollars.

I favor practical experience. Lots of folks are doing this, there's a wide array of experience, shop owners "for offroad use only", 200,000....300,000 miles without issue. It's very common on USMB, a very practical board. I'll need some compelling information to go against a wide base of practical experience from some heavy hitters, like GeneralDisorder on USMB, that are doing this before I go throwing away thousands of dollars.

I'm sure there are hacks trying to throw this thing at cars without proper maintenance. I'm by no means encouraging that, but probably come off that way in my haste and annoyance of the frequency of converters getting quoted/replaced, but bad/poor judgement will exist in every arena, regardless of methods.

I wasn't thinking mostly about carbed EA81's...but 1980's and 90's SPFI EA82's, MPFI EA82's, MPFI ER27's...all of which make high mileages with none of this in place.

It sounds as if you're saying EA engines don't count so that means failing thermostats and fuel mixtures only cause issues with EJ engines and somehow EA/ER engines (Fuel injected or otherwise) are immune to failing thermostats and fuel mixtures? The EA/ER platforms are no less capable of high mileages than EJ engines, so that's not compelling to me.

As you're not a fan of the extender, I'm not a fan of the apocalyptic talk about issues that can only be talked about, not shown or quantified via significant experience. Just because one can surmise a scenario where thermostats kill engines when the 0420 isn't working...doesn't mean it happens or is statistically relevant. At least - that's how I view it, I'm not saying anyone has to agree with me or that you should at all, but again I'm favoring practical experience over technical banter. You're coming from the other side, cool, I'm learning along the way.

I see these things working perfectly fine for 200,000....300,000 miles...it's nearly common place now...not just with Subaru's. But I don't see gobs of failures due to these extenders. Or engines making high mileages because of their impeccable rear O2 sensor performance.

I don't know what the numbers are - but there's a high success rate with extenders - I'm perfect so far (well perfect as far as 200,000 or 300,000 mile Subaru's go if that's enough miles to warrant normal usage) and that's a good fit for many people who can't/won't toss hundreds or thousands of dollars when zero or $10 dollars will last them the life of the vehicle.

to me there's room for both - if folks want to be technical and replace converters , great. if folks want to be more practical, they can join an enormous contingent of folks that have done it successfully.

It is my understanding that the rear O2 sensor is not used by the ECU until around 2005 and up models..or something like that, not all Subaru's?
 

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2010 outback
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Discussion Starter #18
Are you serious? What does it do, clean out deposits?
Do you add 1 bottle of each after each fill up?
Does the check engine go out, or does it have to be reset?
 

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Does the check engine go out, or does it have to be reset?
light should go out on it's own if things move back into specifications.
i would think with that mixture it's going to come back in short order, but hopefully you hear back from him.


cardoc - glad to hear from someone that knows what they're talking about, thanks for sharing.

what do you say about the high number of catalytic converter replacements - that pass emissions/gas analyzer tests? that's my entire platform for this "debacle".

i will not pay thousands of dollars for converters when the ones I have pass a state emissions sniff test/gas analyzer, to me that's just crazy when they easily last the life of the vehicle.

all the other performance/0420 interactions is a separate discussion to me, one I would like to learn more about, and will continue to look at as someone who plans for 300,000 miles out of my vehicles (if rust doesn't get them first LOL) and works on a couple dozen cars a year for others.
 

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GG, you keep throwing around CAT replacement. I have been building/repairing cars 27 years and CAT replacement does not repair an engine performance issue. It masks it. I don't put on band-aids even though it is a high profit quick fix. I don't guess hoping it will fix it.

My experience is, 98% of the time a 420 code pops up, it's not the CAT. 95% of them are something other than an AF or O2 sensor. Sometimes it's something easily repaired like a ground connection. So again, that code does not, I repeat, DOES NOT mean a bad CAT. It means there is a problem with the engine performance.

As for proof, that's why I put it in a thread. I can't video every car that has the code. I video the different scenarios as they pop up and I have a chance to do so. My shop is small and at times so busy I don't get the camera out and shoot it. I'm not running a school all day, its a repair shop, so I have to find it, repair it and get it back to the owner so they aren't without their cars. I only have a few loaners to give out to customers and when one comes in, it's right back out with the next customer, but a lot have to rely on a ride or rental.

I would say that if your H6s are running this bung, and you believe them to be running up to par, supplying all the power they were designed for, I could prove you wrong with 20 minutes of data or less from them. So here is the challenge and it gives you an opportunity to prove your side: You say you repair cars so you have a scan tool available. If not there is free software and a $30 cable available. Record and post two videos of your data. First one from a cold start up at idle for 5 minutes. Second one after the temperature has leveled at operating temperature, usually 15-20 minutes later, running 5 minutes with one minute of the video with rpm at 2700. Post that and I will tell you what I see needs improvement. I would want to see RPM, both AF sensors, MAP, ECT, LTFT, STFT and Calculated Load. That's it for now and those will tell enough.

As for the Alcohol/Cleaner mix. The alcohol breaks up water into molecules that burn easily in combustion. The heavy dose of the cleaner breaks up the carbon and allow it to be blown out the tailpipe. If the CAT has a lot of carbon, the high concentrate will loosen some of it allowing for the CAT to start working again as long as the metals in the CAT aren't already deteriorated. Also, with less carbon in the combustion the engine breaths better. I have always told people use quality gas and add Sea Foam upto 2 times a year to help keep varnish and deposits down. As for light just going out, no. You have to clear it then wait to see if it pops back up after monitor setting since you don't have a tool to watch the data.

Also, I will remind you, I have a Chevy Cavalier with the OE CAT still in place and functioning perfect at 211,000 miles. And I drive it hard. Especially after a ccomplete overhaul and tweaking 75k ago.
 
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