P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)
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  1. #1
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    P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)

    okay so im getting this every day now aprox 4-5 min after startup or 2-3 miles down the road. there are no other codes stored in the ecu.


    so what is the best course of action to diagnose this one

    I'm really hopeing that this is just a sensor problem or at worst a o2 sensor


    I also have heard rumors that there is a ecu flash that does something with the 02 sensor error bounds but i don't know if thats true or if it would even help me


    (car runs fine no smoke nothing out side the norm except the BEEEEEEEP i get every day)

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  3. #2
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    The code thinks your driver side cat is no good, but there is a reflash that fixes a software glitch that triggers this code when there's no problem with the cat. I have the same thing with my '00 V6 and I'm ignoring it for now.

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    I don't think i can ignore it since sooner or later im going to have to pass emssions inspection

    anyone got any ideas of it might be the 02 sensor or not?

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    Quote Originally Posted by y2000passat View Post
    The code thinks your driver side cat is no good, but there is a reflash that fixes a software glitch that triggers this code when there's no problem with the cat. I have the same thing with my '00 V6 and I'm ignoring it for now.
    not quite. that issue throws a p0421 code, NOT this code. i had this happen to me. the issue here that its having is that the oxygen sensors are viewing the activity of the cats and it's seeing that the reaction it's supposd to have is not working as it shoud when the car has just started, but works fine later on. this is a warm-up problem, not a bad cat, so to speak.

    what i would do before all else is head to your parts store, and buy yourself a couple little things of "RXP" they come in a little container about 2" or so tall and 1" diameter. good de-carbonizing stuff here. use one per tank for the next few tanks.

    after the first tank, clear the code by whatever means, and continue with the second tank with another RXP in it. if the code stays away, whoo!
    if not, then would require further diagnosis. stuff costs about $7.99 per unit. good stuff!

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    can you give me a better link to the rxp stuff

    is it similar to seafoam?

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    Quote Originally Posted by crash893 View Post
    can you give me a better link to the rxp stuff is it similar to seafoam?
    http://www.rxp.com/

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    Quote Originally Posted by sipes216 View Post
    not quite. that issue throws a p0421 code, NOT this code. i had this happen to me. the issue here that its having is that the oxygen sensors are viewing the activity of the cats and it's seeing that the reaction it's supposd to have is not working as it shoud when the car has just started, but works fine later on. this is a warm-up problem, not a bad cat, so to speak.

    what i would do before all else is head to your parts store, and buy yourself a couple little things of "RXP" they come in a little container about 2" or so tall and 1" diameter. good de-carbonizing stuff here. use one per tank for the next few tanks.

    after the first tank, clear the code by whatever means, and continue with the second tank with another RXP in it. if the code stays away, whoo!
    if not, then would require further diagnosis. stuff costs about $7.99 per unit. good stuff!
    I thought the p0421 and p0431 codes were the same problem - one for the driver side cat, and one for the passenger side cat. That said, I've heard others suggest the RXP. I've looked for it but don't find it at local auto parts stores so I'll need to order it. BTW, the applicable technical service bulletin for the reflash is TSB 05-13.

  9. #8
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    is that something that they should do for free ( the reflash?)

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    complements of http://passatb5.wikidot.com/obdii-codes


    # P0420 Catalyst System Efficiency Below Threshold (Bank 1)
    # P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
    # P0422 Main Catalyst Efficiency Below Threshold (Bank 1)
    # P0423 Heated Catalyst Efficiency Below Threshold (Bank 1)
    # P0424 Heated Catalyst Temperature Below Threshold (Bank 1)
    # P0430 Catalyst System Efficiency Below Threshold (Bank 2)
    # P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)
    # P0432 Main Catalyst Efficiency Below Threshold (Bank 2)
    # P0433 Heated Catalyst Efficiency Below Threshold (Bank 2)

  11. #10
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    and lastly if it was a bad cat wouldn't i be getting other codes too saying that they cats weren't working after the temp got up?

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    Try this:

    Clear the codes at night, let it cool all night. Next day, when you start to drive it, drive as smoothly and easily as possible. If the light stays off, it's going to be an O2 sensor most likely. A bad O2 can give false readings itsef as it warms up which aren't enough to trigger an O2 CEL but are off enough to make the ECU think there's a cat problem.

    I had both post-cat sensors replaced (maybe all 4 TBO) and the problem hasn't come back. With only ~65k miles on my cats at the time, I knew they couldn't be bad themselves.

  13. #12
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    Got the RXP at AutoZone (Thomas knows his stuff!)

    You guys should also get the obscure recomm. by our silver bullet:
    Bullit62:
    The upgraded OEM Oil Filler Cap! around $30 to RELIEVE PCV Pressure!!

  14. #13
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    Quote Originally Posted by 02GLXWag6stk View Post
    Got the RXP at AutoZone (Thomas knows his stuff!)

    You guys should also get the obscure recomm. by our silver bullet:
    Bullit62:
    The upgraded OEM Oil Filler Cap! around $30 to RELIEVE PCV Pressure!!
    what the hell are you talking about son?

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    Quote Originally Posted by crash893 View Post
    what the hell are you talking about son?
    I believe Anson's referring to this: http://www.ecstuning.com/Volkswagen-..._Cap/ES258817/


    And FWIW, I also believe he's old enough to call YOU son...

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    Quote Originally Posted by crash893 View Post
    what the hell are you talking about son?
    Spoken like a WANNABE!

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    Quote Originally Posted by Bullit62 View Post
    I believe Anson's referring to this: http://www.ecstuning.com/Volkswagen-..._Cap/ES258817/


    And FWIW, I also believe he's old enough to call YOU son...
    Touche

    And now I understand from my long meeting last night with an aircraft engine mechanic why you are a SilverBullet

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    Curious, are you two purporting that a venting oil cap will clear his catalyst inefficiency CEL?

  19. #18
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    Dave,

    The commentary was a SUPPLEMENTAL bene to the V6 respondees
    vs the OP's comprehension!

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  21. #20
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    so im still a little in the dark about how we started talking about oil caps and how a oil cap would solve a cat problem

    but i have good news

    apparently a little bit of the old Italian tuneup and some new gas did the trick.

    I haven't gotten a CEL for a few days now (fingers crossed)

  22. #21
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    So its back ....... or it was for the last 1/4 of a tank of gas.

    I switched to a test tank of 93oct and it went away almost immediately.


    any ideas on if this is actually gas related or if its just a coincidences.

    I was thinking my fuel filter is getting a little up there in age could it be that?

  23. #22
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    My V6 did the same thing almost exactly. I would always have a CEL after filling with any grade fuel from Rotten Robbie, too.

    New O2's did the trick.

  24. #23
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    Had this happen on my V6 A4 and the cat was replace buy Audi free of charge as I was under 80k. This is only an early sign of a cat going bad. If you are under 80k I would get it to a dealer and checked out.

  25. #24
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    115k so no go

    did you replace the pre or post 02?

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    VW replaced both the Bank 1 Sensor 1 and Bank 2 Sensor 1. Those should be the fronts.

    Checking my paperwork just now, I see that I was also getting codes for the fronts as well, not just the catalytic converter inefficiency codes. Although when I scanned with VAG-COM the first few times, the inefficiency codes were all that I had.

    edit: Also, my CEL was very consistent. Any heavy throttle on a cold morning especially would trigger the light like clock work. Over 6 months and 5k miles since the repair, the CEL hasn't been on once.

  27. #26
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    Mine i feel is a little different

    after 4-5 min no matter what (idle , hauling ass, normal driving)

    but it is going away with 83 octane so i'm thinking that either i need to run some injector cleaner or something else through the system and go back to 81 and see if that fixes it

  28. #27
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    83 and 81? Do you fill up in Mexico?

  29. #28
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    I always forget which one is which

    whatever the lowest american one is

    I think its 83 87 93 something like that

    I tested with 87 and it went away
    i normally run 83 (lowest) and have been for about 7 years with out issue)
    something is afoot

  30. #29
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    Quote Originally Posted by crash893 View Post
    So its back ....... or it was for the last 1/4 of a tank of gas.

    I switched to a test tank of 93oct and it went away almost immediately.


    any ideas on if this is actually gas related or if its just a coincidences.

    I was thinking my fuel filter is getting a little up there in age could it be that?
    Quote Originally Posted by TheAmazingDave View Post
    My V6 did the same thing almost exactly. I would always have a CEL after filling with any grade fuel from Rotten Robbie, too.

    New O2's did the trick.
    I've found that as long as I keep using 91 from Shell, the light stays off for much longer intervals...

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