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Guest Message by DevFuse

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1996 Subaru Legacy Outback Wagon P0420 engind code

Check engind P0420

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7 replies to this topic

#1 jada32819



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Posted 22 February 2014 - 12:07 PM

I have a 1996 Outback with 2.5 engine , has P0420 code, any suggestion , there are no any other code for engine misfire

#2 Legacy777



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Posted 23 February 2014 - 07:19 PM

Welcome to the USMB.

I'm going to move your thread to the new gen forum.

#3 Suzam


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Posted 23 February 2014 - 08:19 PM

How may miles on the car?


A p0420 can be the result of a o2 sensor getting lazy. If it's running fine you can reset it if the CEL is still on and see if it returns.


I had one that would pop the CEL after a highway run at higher speeds every 6 months or so. I'd just reset it since it ran fine and there was no drop in MPG. As long as it was well before the emission check the car still passed without trouble.

#4 luko


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Posted 23 February 2014 - 08:34 PM

What is the vehicle's history?  such as any new parts on it?

#5 Sdam87



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Posted 02 March 2014 - 10:50 AM

Probably a poop'd out o2 sensor, or you need a cat.. If I remember right, the 420 codes are cat related. And or stoner related.. heyoh! haha 

Edited by Sdam87, 02 March 2014 - 10:51 AM.

#6 1 Lucky Texan

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Posted 02 March 2014 - 01:30 PM

there are many things that can cause that code. even exhaust leaks.


#7 luko


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Posted 02 March 2014 - 06:30 PM

Catalyst efficient code...Remember catalytic converters just don't go bad...something causes them to go bad, so if you just slap a new set of cats on it chances are you'll have the same problem down the road 

#8 idosubaru


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Posted 03 March 2014 - 07:28 AM

how long have you owned it?

when were the headgaskets replaced?


annoying code.  there's about 1,000 things that can cause it.

best off just ignoring it.  being a 1996 you can get an exemption from emissions due to a 1996 specific issue. 

so it shouldn't matter at all if the check engine light is on.


fix any exhaust leak

seafoam the intake

fuel additive

new NGK OEM plugs

New OEM wires


you're not likely to find a mechanic capable of properly diagnosing what is causing it so they'll usually just throw a new catalytic converter and O2 sensor at it even though that's not likely the cause.

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