Codes: P0420, P0171, P0171 Pd
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This is a discussion on Codes: P0420, P0171, P0171 Pd within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; P0420: Catalyst efficiency below threshold (bank 1) P0171: System too lean (Bank 1) P0171 Pb: system too lean (bank 1) ...

  1. #1
    Registered User phernic's Avatar
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    Codes: P0420, P0171, P0171 Pd

    P0420:
    Catalyst efficiency below threshold (bank 1)

    P0171:
    System too lean (Bank 1)

    P0171 Pb:
    system too lean (bank 1)

    These are the codes i pulled today, and what do they mean. 2004 WRX with 50,781 miles, perrin short ram intake and axle back exhaust.

    thanks!

    -vic-

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    Registered User EvoEatr's Avatar
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    The P0171 (P0171pd means the code is pending) is most likely because you have the aftermarket intake on the car....As for the P0420 do you have anything else done to the exhaust? catless up-pipe/downpipe? Do you have any kind of tune/engine management on the car?

  4. #3
    Registered User phernic's Avatar
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    Quote Originally Posted by EvoEatr View Post
    The P0171 (P0171pd means the code is pending) is most likely because you have the aftermarket intake on the car....As for the P0420 do you have anything else done to the exhaust? catless up-pipe/downpipe? Do you have any kind of tune/engine management on the car?
    No catless pipes of any kind, and no tune or engine managment. I took my WRX to AndrewTech (awesome dudes) in Maryland and all they did was lift the O2 sensor out of the cat (instead of using one washer, they used two to bring it alittle out of the cat...not sure how to explain that) . buddy of mine just said those P0171 codes wont go away till you get some kind of tune or engine management. is that true? if so, i just got some leverage to convince the wife to get me some sort of engine managemt!

  5. #4
    Registered User phernic's Avatar
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    when I get time, I am going to check the cat and O2 sensor. Any suggestions on what should be done to trouble shoot the problem?

  6. #5
    Registered User EvoEatr's Avatar
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    Well Yes chances are you wont get he P0171 gone until you get some form of tune/engine management unless of course you put the stock intake back on...as for the 02 Sensor why on earth did they remove the sensor and add a washer? As of now I believe that is what is throwing your P0420 because A: I find it extremely hard to believe a simple axle back exhaust would throw this B: It happens, but is somewhat unlikely your cats would be going bad at around 50k (they are SUPPOSED to last the life of the car)... Was the 420 code present before they modified" the 02 sensors position?

  7. #6
    Registered User phernic's Avatar
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    yes, the P0420 code was there before they tried to fix it and it keeps coming back.

  8. #7
    Mace Windu devilfluff's Avatar
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    If the cat is failing, it is warrantied 8 years or 80,000 miles.
    Dirty Jersey
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  9. #8
    Registered User EvoEatr's Avatar
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    As pointed out cat. converters are covered for a lengthly amount of time...Insted of messing with it I would prob just bring the car to the dealer and see what they say..not to sure how they will react to aftermarket parts though...

  10. #9
    Registered User phernic's Avatar
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    guess i will suck it up and take it to the dealer....hope it doesnt cost that much...thanks guys!

  11. #10
    Registered User EvoEatr's Avatar
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    no prob man...if they tell you you need new cat. converters it should be covered...I know Subaru just instituted a new policy for warranty cat. converters though...before condemning the cat conv. when a P0420 appears...the technician must go through a series of tests to rule out other possibilites of the code setting...( I guess Subaru was getting to many come-back cat. problems or something) let us know what they find out....

  12. #11
    Registered User phernic's Avatar
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    quick thought,

    could I just get an aftermarket midpipe and axle back exhaust (completly new set)? I have plenty of money set aside for my car, so, would that help the 420 code? if so, what would be a good midpipe without throwing emisions?
    Last edited by phernic; 04-21-2009 at 10:22 AM.

  13. #12
    Mace Windu devilfluff's Avatar
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    The vehicle has a cat in both the midpipe & the downpipe.

    If you want to go catless, I would reccomend an engine management system(UTEC, AP, etc) and replacing the uppipe as well.
    Dirty Jersey
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