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brucey · 12-30-2010, 04:38 AM

I've lived with my P0420 code for several years now. You just turn it off when the light comes on. Doesn't affect mileage. I'm pretty sure if you clear the code right before emissions test you'll even pass it. Basically it's just the redundant 02 sensor saying it's not reading exactly as it should, but it COULD also be the cat/front sensor. I say find a way to turn it off (unplug the battery if you don't have a code scanner/scangauge) and see how it affects your mileage. If there is no real change (I know winter is not nearly as consistent for me) then it's nothing to worry about, really.

PS: All this info is based on my own experiences with subaru, but an engine is an engine.

12-30-2010, 04:38 AM	#2 (permalink)
brucey A madman Join Date: Mar 2008 Location: WV Posts: 1,018 Pequod - '17 Subaru Outback 90 day: 22.79 mpg (US) Thanks: 73 Thanked 183 Times in 98 Posts	I've lived with my P0420 code for several years now. You just turn it off when the light comes on. Doesn't affect mileage. I'm pretty sure if you clear the code right before emissions test you'll even pass it. Basically it's just the redundant 02 sensor saying it's not reading exactly as it should, but it COULD also be the cat/front sensor. I say find a way to turn it off (unplug the battery if you don't have a code scanner/scangauge) and see how it affects your mileage. If there is no real change (I know winter is not nearly as consistent for me) then it's nothing to worry about, really. PS: All this info is based on my own experiences with subaru, but an engine is an engine.