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Old 07-10-2009, 07:12 PM   #1
SubieChick05
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2014 WRX
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Default P0420 ?

Hey guys I'm hoping someone could help me out here! When I put my downpipe on my check engine light came on about 2 weeks later.. throwing code P0420. I know its the cat efficiency code but my question is.. does this mean my o2 sensor is bad? or could I be throwing that code because I don't have a tune on my car yet? I heard somewhere it could be because of not having a tune but then I also saw some posts on here about it being the o2 sensor. I don't know too much about these things so if someone could help me out it would be greatly appreciated!!

Thanks
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Old 07-10-2009, 07:16 PM   #2
munkis
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Did you put a catless exhaust on. If you did you are getting the code because you have no more cats.

If you get tuned they can flash out the codes so the light doesnt come on.
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Old 07-10-2009, 07:23 PM   #3
SubieChick05
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Yeah I have turbo back Invidia exhaust so I know about the cats.. just wanted to know if it was a problem with the o2 sensor so I know whether or not to replace it..

Should be getting a tune here in about 2 weeks!!!
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Old 07-10-2009, 07:58 PM   #4
cobra killa
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what sets off a P0420 is when the output from the front and rear O2 sensors are more or less equal. This shows that the gases leaveing the cat are almost the same concentrations as they were before they entered the cat. if the cat is bad most dealerships give warranties so being a subaru my guess is 8 year 80,000 miles most likely it is a cat. Soooo... if there is no cat the outputs are the same so the car throws a code!!! any more questions?
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Old 07-11-2009, 04:20 AM   #5
bue car
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sensor is fine, i have a spacer you can use to pull the sensor out of the exhaust a little.
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Old 07-11-2009, 05:31 PM   #6
SubieChick05
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Thanks for the answers!!
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