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Discussion Starter · #1 ·
Hi everyone

I took my 2003 outback into my usual mechanic for P0420 codes and he replaced the Catalytic Converter. Check Engine light came back on only two days after, so I ran the codes and got P0420 again. I cleared them and chalked it up to the new CC needing a few days. I am not noticing any performance issues and after 17 days the P0420 codes popped up again. I've done some research and it looks like it could be the o2 sensors? I am not getting any other codes though, wouldnt a faulty o2 sensor have a code of it's own? Any advice appreciated, thanks:)
 

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2012 OB , 2017 Impreza
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It is all too easy for mechanics to guess the cause of a problem and throw parts at it... they do not have to pay for the parts....AND they get paid to do the work.

The proper and correct method to FIX this (or any other) problem is to TROUBLEHOOT and identify the cause.... not to fire the parts-cannon at it. Any competent mechanic should have such skills.

Modern cars make it pretty easy to do such troubleshooting... just plug into the OBDII connector underneath the dashboard and graph the vital sensor signals.
 

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2010 Outback 3.6R 2014 Legacy 2.5i
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data log it and verify that your rear 02 sensors are working correctly also verify that lambada is correct (AFR)
 

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Discussion Starter · #4 ·
It is all too easy for mechanics to guess the cause of a problem and throw parts at it... they do not have to pay for the parts....AND they get paid to do the work.

The proper and correct method to FIX this (or any other) problem is to TROUBLEHOOT and identify the cause.... not to fire the parts-cannon at it. Any competent mechanic should have such skills.

Modern cars make it pretty easy to do such troubleshooting... just plug into the OBDII connector underneath the dashboard and graph the vital sensor signals.
Hi thanks for the response. I'm not sure how to graph the vital sensors with my OBDII? I cleared the P0420 code again and went to the Diagnostic menu and here is what I've got. I hope this helps.
Communication Device Fluid Telephony Satellite phone Gadget Communication Device Fluid Gadget Telephony Portable communications device Telephony Fluid Communication Device Finger Portable communications device
 

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Discussion Starter · #5 ·
data log it and verify that your rear 02 sensors are working correctly also verify that lambada is correct (AFR)
THanks for replying! How do I data log it? Is that something that i can do with my obdII? I have no idea how to check the AFR or do any of this.
 

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Discussion Starter · #7 ·

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2012 OB , 2017 Impreza
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THanks for replying! How do I data log it? Is that something that i can do with my obdII? I have no idea how to check the AFR or do any of this.
Your little scanner may not be able to 'log' data... but may be able to monitor 'live data'.
The screenshots you are showing are simply the final RESULTS of the computer detecting an out-of-tolerance condition....the 'live data' (if your scanner can do it) would be under a different selection.
 
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