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Thread: 17584 - Bank1: O2 (Lambda) Correction Behind Catalyst

  1. #1
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    17584 - Bank1: O2 (Lambda) Correction Behind Catalyst

    Evening all,

    Forgive me for posting in this section with my Mk4 R32 (86k on the clock) troubles but this is where the cool kids hang out

    In all seriousness I know there are a few members in this section who will most likely know the answer to the problem.

    About 3 weeks ago I fitted a de-cat system to the R32 and as expected 40 miles later the engine light came on. It was booked in for an R-Tech map the following week so I wasn't worried about it and didn't even check the fault code as I knew it would be relating to the missing cats.

    After my R-Tech map Niki coded out the rear lambda emission part and off I went.

    About 300 miles later I hit a bump on the motorway and literally a second later I got a beep and the EML come on again.

    I scanned the car and I had these codes: -

    17584 - Bank1: O2 (Lambda) Correction Behind Catalyst
    P1176 - 001 - Control Limit Reached - MIL ON
    16538 - Oxygen (Lambda) Sensor B2 S1
    P0154 - 008 - No Activity - Intermittent


    I thought one of them would be a left over code related to the de-cat so I cleared them to see what (if any) came back.

    Well approximately 300 miles later the EML has come on again and I only have this code now: -

    1 Fault Found:
    17584 - Bank1: O2 (Lambda) Correction Behind Catalyst
    P1176 - 001 - Control Limit Reached - MIL ON


    Looking it up on Ross-Tech wiki suggests the following: -

    Possible Causes

    • Intake Air System leaking
    • Oxygen Sensor(s) and/or Oxygen Sensor Control faulty

    Possible Solutions

    • Check Intake Air System for Leaks (False Air)
    • Check Oxygen Sensor(s) and/or Oxygen Sensor Control (all of them!)

    Is my main option here to replace the lambda sensors?

    Does anybody know what side/sensor bank 1 refers to?

    Thanks in advance

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  3. #2
    Yohan87's Avatar
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    Okey dokey, getting somewhere now.

    Reply from Awesome GTI

    "I think for starters with this one we would need to have a look at it and check the software version. just one thing stands out with it saying bank 1. This means it would be the pre cat sensor anyway so nothing to do with a de cat! Usually the sensor or the actual wiring to the sensor."

    Gonna replace my pre-cat lambdas and take it from there.

    Out of interest, does anyone know what code you normally get from de-catting?

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    RIP S3dave

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    erm nope.. it does'nt mean that.

    Bank 1 is a side.. Sensor 1 is control lambda. Sensor 2 is post cat one
    you have 2 banks being the R32


    your first error code does say sensor 1 tho.. which is a controlling lambda not an emissions car related one
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    Yohan87's Avatar
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    Thanks for clarifying Bill.

    So is Bank 1 drivers side?

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    Yohan87's Avatar
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    Maybe this code is related to the original 16538 code as that was a pre-cat issue but on the other bank.
    Last edited by Yohan87; 18th September 2013 at 11:32.

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    Quote Originally Posted by Yohan87 View Post
    Thanks for clarifying Bill.

    So is Bank 1 drivers side?
    hmm
    I dont know off hand, sorry
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    Speak to Nick at RTech about it.

    Given it specifically says "behind catalyst" it sounds like something in the post-cat o2 delete isnt right?

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    Yohan87's Avatar
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    From what I've read...

    Bank 1 - The side where Cylinder #1 starts so Drivers side (offside)

    Bank 2 - Opposite to the above, so Passenger side (nearside)

    Sensor 1 is a control lambda (pre cat)

    Sensor 2 is post cat one

    Lambda Sensor Part Numbers

    N/S/F Probe (Bank 2 / Sensor 1) - 1K0 998 262 M
    N/S/R Probe (Bank 2 / Sensor 2) - 1k0 998 262 B
    O/S/F Probe (Bank 1 / Sensor 1) - 022 906 262 Q
    O/S/R Probe (Bank 1 Sensor 2)- 1K0 998 262 R

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    Quote Originally Posted by aragorn View Post
    Speak to Nick at RTech about it.

    Given it specifically says "behind catalyst" it sounds like something in the post-cat o2 delete isnt right?
    Have done mate, he said it's a routine he's used on several R's without any problem. He also said it's a very rare fault code to get.

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    "Stick a V8 in it!"

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    It seems its definitely related to the post-cat delete though:

    Post Cat Correction - 2001 Audi S4

    Essentially what thats saying, is the post cat lambda is used as an adjustment on the main fuelling control, and if its not disabled properly you get weird fuelling and errors like the one you've got.
    Last edited by aragorn; 18th September 2013 at 12:55.
    Yohan87 likes this.

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    Quote Originally Posted by aragorn View Post
    It seems its definitely related to the post-cat delete though:

    Post Cat Correction - 2001 Audi S4

    Essentially what thats saying, is the post cat lambda is used as an adjustment on the main fuelling control, and if its not disabled properly you get weird fuelling and errors like the one you've got.
    Interesting.

    I notice a lot of those guys physically unplug their sensors, mine are definitely still connected.

    Do you think unplugging them would change things?

    I'm 100% confident Niki mapped them out properly.

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    Well if your getting that code, then I dont think they are mapped out correctly.

    If they were mapped out correctly, post cat lambda correction would be turned off, and its clear that in your case, its not, because your getting codes for it.

    However yes, going on the first few posts of that thread, if you unplug them it should stop it having the correction effect. Give it a try.

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    I'll unplug them tonight, clear all codes and report back with how it drives and what happens. Thanks for your help so far

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    Quote Originally Posted by Yohan87 View Post
    I'll unplug them tonight, clear all codes and report back with how it drives and what happens. Thanks for your help so far
    Niki said unplugging them shouldn't matter.

    I've got nothing to lose by trying though I guess.

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    "Stick a V8 in it!"

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    Are the sensors still in the exhaust?

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    Adaption may not work if unplugged.... even fully coding them out sometimes doesn't work from the stuff I have read... never had the issue personally as I always leave the post cat sensors connected...

    If you unplug them check blocks 001 and 032

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    Quote Originally Posted by aragorn View Post
    Are the sensors still in the exhaust?
    They are.

    Quote Originally Posted by <tuffty/> View Post
    Adaption may not work if unplugged.... even fully coding them out sometimes doesn't work from the stuff I have read... never had the issue personally as I always leave the post cat sensors connected...

    If you unplug them check blocks 001 and 032

    <tuffty/>
    I was thinking on the way home today actually, surely if it was emissions related it would affect both banks as there is a cat for each?

    What should I be seeing in 001 and 032? Is this at idle I should check?

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    Quote from Niki.

    "In the map the eobd euroswitch for cat monitoring gets switched to 0. This turn off all related issues from running a decat. It's what all tuners use at stage decat me7 me7.5 med9 ecu all same. If there is any fault bring up dash light relating to and of the S2 sensors then it's a fault with a sensor, air leak or another fault.

    S2 routine can be fully mapped out and even have sensors fully removed to mask faults or to save replacing a naff sensor.

    This cannont effect power at all. They are monitor sensors not control".

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    so is that suggesting that even tho its mapped out, you still need fully functioning sensors for whatever reason?

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    Yeah seems only a very small part relating to the cat bit is mapped out. If anything else it is monitoring goes out of range then a fault is still thrown.

    Problem is, mine only says Bank 1, doesn't specify S1 or S2 which is annoying.

    It's all very well mapping them out completely but to what effect on the fuelling etc? They must have some controlling functionality.

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    Wee update on this.

    Measured block 032 with all the probes connected and they all read 0.0%.

    The code keeps coming back every few hundred miles but this time I had a code for Bank 2 beside it. The only difference is Bank 2 said Control Limit Reached - Intermittent.

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    "Stick a V8 in it!"

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    The bit Niki seems to be missing is that they are NOT just monitoring sensors. Some cars use rear O2 for fuelling correction. Yours is one of them.

    He has disabled Cat monitoring, but he has not disabled Rear O2 lambda control. Read the post i linked earlier from Nefmoto.

    If they are properly deleted, turning off ALL the rear O2 controls, you would not be getting these codes, and you could happily remove the sensors and throw them away.

    Another link to Rear O2 delete info here (specific to the S4, but the same will apply to your engine):

    Tuning - S4wiki


    If your fuel trims are reading 0.0% then they're not working, however i suspect you read these immediately after clearing fault codes, and clearing codes resets the LTFT's so they would show 0.0% until you'd drove around a bit.

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    Quote Originally Posted by aragorn View Post
    The bit Niki seems to be missing is that they are NOT just monitoring sensors. Some cars use rear O2 for fuelling correction. Yours is one of them.

    He has disabled Cat monitoring, but he has not disabled Rear O2 lambda control. Read the post i linked earlier from Nefmoto.

    If they are properly deleted, turning off ALL the rear O2 controls, you would not be getting these codes, and you could happily remove the sensors and throw them away.

    Another link to Rear O2 delete info here (specific to the S4, but the same will apply to your engine):

    Tuning - S4wiki


    If your fuel trims are reading 0.0% then they're not working, however i suspect you read these immediately after clearing fault codes, and clearing codes resets the LTFT's so they would show 0.0% until you'd drove around a bit.
    I'll forward him the link to this thread so he can speak for himself as it wouldn't want to say the wrong thing.

    I know he has definitely disabled CDKAT.

    The good news is from what you've posted that it certainly looks like they can be mapped out however this raises another questions for me...

    Since it appears that the rear O2s are used for control from the links you've posted then what effect does disabling them completely have on the running of the car?

    Does the ECU then just resort to a "default" set of values in absence of any feedback from the rear lambdas?

    The trims were read straight after clearing the fault codes. I'll re-read them after I put a couple of hundred miles on it again.

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    "Stick a V8 in it!"

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    The ECU simply uses the main (front) O2 sensors on their own when the rears are disabled.

    I suspect your fault exists because one of the rear O2's is actually faulty, and is feeding garbage back to the ECU. The ECU is acting on this garbage, then eventually running out of adaption and popping the fault code.

    So potentially the problem could be fixed by replacing the faulty O2 sensor. However if it was my car, i'd rather the rear O2's were simply disabled altogether, as its a waste of money replacing sensors that arent really needed.

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    Quote Originally Posted by aragorn View Post
    The ECU simply uses the main (front) O2 sensors on their own when the rears are disabled.

    I suspect your fault exists because one of the rear O2's is actually faulty, and is feeding garbage back to the ECU. The ECU is acting on this garbage, then eventually running out of adaption and popping the fault code.

    So potentially the problem could be fixed by replacing the faulty O2 sensor. However if it was my car, i'd rather the rear O2's were simply disabled altogether, as its a waste of money replacing sensors that arent really needed.
    Agreed.

    It would be easier if it just said B1 / S2 faulty but alas it doesn't.

    If you're theory is correct then the car should actually run better with the rears disabled?

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    "Stick a V8 in it!"

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    Well if its feeding in garbage and messing with the fuel trims, then sure, it should run better with it fixed!

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