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CEL: Code PO420: "Catalyst System Efficiency Below Threshold"


Hanger

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For the past 2 months I've got CEL and Cruise blinking on me 3 times, went off twice right before I arrive at the dealership :mad: :mad: :mad:

 

 

Now I finally got it here with it still blinking...

 

My car is 2005 Subaru Legacy 2.5i w/ 64,000 miles

 

No exhaust mods except a pair of Prodrive Axlebacks... Dealer said that it's either the Catalyst converter or the O2 sensor. The Catalyst converter will be covered under 8year/80,000 miles emission warranty, but they will need my car for the whole day to do some testing and they won't replace any parts until SOA examine the data and approve for it :(

 

Do you guys know what might cause this? Does this mean I should get a custom catback now? :lol:

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Instagram: itshangertime :spin::spin::spin: ○ ○ ○

 

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i had the same code on mine too. happened about 3 months ago twice. came and went a little after i filled up. thing is mine only had like 23k miles. mine is pzev. i read somewhere that too much ethanol in gas increases emissions. so i figure where i pumped up had a little to much which caused increased emissions which tripped the check engine light? i don't know just a guess, because it hasn't been back since.
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  • 2 weeks later...

I am having the issue as well, it happened twice today and both times were after filling up!

I just detuned from STGII ( where the car has been for 2 years/45k miles) just to see what the car does stock and what kind of power I lost without the tune ( and try to improve some fuel economy).

not crazy gains in fuel, but I did gain two CEL's boooo

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