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Oxygen Sensor Question - P0420 Code


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Hello,

So I was driving to work the other day and my CEL light came on. Code P0420. Car is a 2008 Legacy, has the 2.5 N/A motor, 86,000 miles, 4 speed auto, so I know it's likely an oxygen sensor. Is there any particular brand oxygen sensor that seem to work better in our cars? Any brands to avoid?

 

My other vehicle, a 1997 Dodge Ram, is picky about what brand sensors go in and just didn't know if Subaru was the same way.

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Buy Denso found here:

http://www.rockauto.com/catalog/moreinfo.php?pk=1607136&cc=1440455&jnid=393&jpid=3

 

They are great OEM replacements dont require any wire cutting like a universal O2 sensor.

 

If you continue to get the P0420 your catalytic convert might be going bad. on our cars this used to be a VERY expensive replacement luckily Walker and Bosal stepped up and started making cost effective replacements

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  • 3 months later...
I'm in the same boat and considering options related to cat replace. I'd appreciate any info. I just replaced both O2 sensors and am still p0420. Tuning is all new to me?!? What is a fair price for a cat? I also heard a rumor that 05 legacy 2.5 might be part of a cat recall. Does that mean I should hit up the dealer as next step?
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I am asking about an 07 Legacy wagon with about 150K miles and 5speed.

We have the P0420 coming on regularly, we clear it and it comes on again.

I am curious if you have excessive oil consumption and if you have taken a look at the inside of the tailpipes. If you dab a finger in there, does it come out powdery black?

Thanks

George in Lion's Head, Ontario

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if the cat is dead its dead, the code will keep coming back. depending on your location, just delete it and tune the code out. or replace it with your most affordable option, likely having a cat welded in by a professional shop.
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My learning experience continues...and has been less than pleasant. My 2.5 is apparently the H4 super low emissions vehicle, having 3 cats. Since I'm pushing 155k on the odometer, I'm suspecting that all 3 cats could be in need of replacement. Bought this car in the lane at auction (which I never do w/o a more careful inspection) to be my winter get-around. Had no CEL on at the time (dealer probably cleared code prior to running through the lane). Ive already replaced 2 driveshafts, both O2 sensors, rims/tires, OEM floormats, and all swaybar links. Nice car...but is quickly becoming a $$$ pit!
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I am asking about an 07 Legacy wagon with about 150K miles and 5speed.

We have the P0420 coming on regularly, we clear it and it comes on again.

I am curious if you have excessive oil consumption and if you have taken a look at the inside of the tailpipes. If you dab a finger in there, does it come out powdery black?

Thanks

George in Lion's Head, Ontario

 

Actually, my engine doesn't excessively burn oil (knock on wood), but it is common with these engines to have oil consumption issues. If you are consuming oil, then yeah, your cat is probably getting clogged up.

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Some states require dealers to warranty Cats outside of the manufacturer and federally mandated replacement timeframe. I know a few states in my area require 10 years 80k and others are 10 years 100k

 

If you're nice to the dealer they might replace them with 86k. Subaru is usually pretty good about this stuff. The key is being nice to the dealer and any SOA rep you speak with.

 

I've seen SOA replace cats at 6 years 100k for several customers.

Need forum help? Private Message legGTLT
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My local dealer stated over the phone that the "emissions system" (whatever that means) is covered up to 157k on my car...

 

Sounds like a random number to me, but I made an appointment with them for next week anyhow. Worth investigating prior to reaching into my pocket for replacement. I'll keep you posted.

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Same prob with my 08 legacy i just installed a 10$ o2 spacer and fix the problem for now. But dont change your o2 and dont get and get an aftermarket cat either. Best solution is either get a good used OE cat or new OE cat. Cause aftermarket cats sucks they usually fail in 2yrs.
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So here is an update...

My local dealership ordered my OE cats today. They will be replacing them FREE OF CHARGE as part of recall/warranty program. Of course they are attempting to sell me into some additional exhaust work at an estimated $1000. However, I'm politely declining the additional work (my exhaust guy can replace pipe and make some welds at flanges for a few hundred bucks). They are also replacing airbag as part of an earlier recall. Also inspected brakelines (which were good to go).

 

I have to say that I am shocked that the dealership has provided such a generous offer on a car that just turned 155k. I keep thinking there's got to be a catch! Car goes back into the dealership in a couple of weeks.

 

Stay tuned!

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  • 3 weeks later...

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