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Discussion Starter · #1 ·
I bought a used 04' Outback H6 LLBean which has been consistently given me the PO420 code since 2 weeks after I bought it. Initially the dealer I bought it from shrugged off the code, which I initially did, and after it turned itself off for a while I was optimistic; however the code inevitably came back on and has been steadily on for the better part of the last 6-7 months. Had one other mechanic diagnose it and he gave me a quote of $1800 to replace the front two cats (ouch). Dismayed, I got a second opinion. Mechanic #2 said, after looking at the firing order of the cylinders, said only the right-side(passenger) cat needed to be replaced at a cost of a little over $600. Naturally I'm hoping Mechanic #2 is correct. I don't feel like paying a repair cost of 40% of what I paid for the **** car.

Okay experts, who is right? I want this thing resolved before I hit the road this summer.

-R
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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27,165 Posts
how about you find a mechanic not so interested in dumping perfectly good expensive cat converters.

and find what thing is causing a p0420 that is cheaper.

like a rear "downstream" o2 sensor. (the ones to buy are denso branded ones, typically off rock auto/ amazon,...as local parts stores like to overcharge for them). rock wants $48 (find a 5% off coupon code ).
https://www.rockauto.com/en/moreinfo.php?pk=991759&cc=1426867&jsn=357

how many miles you got on this.? are you running high octane gas now?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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27,165 Posts
and is the exhaust loud? like it has a leak in front of the cats, or at the cats? (such makes for "too much oxygen" and a 0420 code).
 
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Meh.
I has wagons.
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12,382 Posts
Hey guys, I think the search is broke again.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
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27,165 Posts
Hey guys, I think the search is broke again.
the way things really are the forum should just open to a decision making matrix.

like: what is your problem ? (head gaskets/ cooling, p0420, tires/ wheels,...rust,
bird crap, beer farts, eyesight, battery, new car audio,.
..portable meth lab shorting out 2017's car audio.).
 

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2012 OB , 2017 Impreza
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3,870 Posts
It is a little known fact that catalytic converters can be CLEANED.

My daughter's 2006 Outback was throwing P0420. I reset it many MANY times and it would always come back.

Her mechanic did the following:
1) Carefully remove Cat to prevent damaging the flanges.
2) Soak the Cat in some kind of liquid 'cleaner'
3) Reinstall Cat and drive for awhile to burn off the 'cleaner'
4) Install new O2 sensor behind Cat. (the 'cleaner' may contaminate it)

The P0420 has NOT returned.
 
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