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  1. #1
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    Default O2 sensor downstream after decat.

    Student car # 1 a 2016 Peugeot 308 1.2T threw an engine light a while back, Son took it to West Vaal Peugeot in PTA they diagnosed a faulty O2 downstream ( after the Cat) sensor and cleared the code.

    Car was fine for two weeks and the code came back, and with it the limp mode. So now we booked it it to have the O2 sensor replaced as suggested by Peugeot. ( aftermarket warranty said yes)

    However, this car has had its cat removed by the previous owner. I had my suspicions but it was confirmed that it has no catalytic converter.

    So my question is, will it not continue to throw a code with a new downstream O2 sensor because there is no Catalytic converter ? You tube tells me that the downstream O2 sensors job is to indicated if the cat is working correctly.

    Bought the 5 months ago and he did about 4000km before this issue.

    The de cat does look like a professional job. Nicely welded piece of stainless steel pipe where the Cat was.

    Karol Life = Σ(Choices)
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  2. #2
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Karol View Post
    Student car # 1 a 2016 Peugeot 308 1.2T threw an engine light a while back, Son took it to West Vaal Peugeot in PTA they diagnosed a faulty O2 downstream ( after the Cat) sensor and cleared the code.

    Car was fine for two weeks and the code came back, and with it the limp mode. So now we booked it it to have the O2 sensor replaced as suggested by Peugeot. ( aftermarket warranty said yes)

    However, this car has had its cat removed by the previous owner. I had my suspicions but it was confirmed that it has no catalytic converter.

    So my question is, will it not continue to throw a code with a new downstream O2 sensor because there is no Catalytic converter ? You tube tells me that the downstream O2 sensors job is to indicated if the cat is working correctly.

    Bought the 5 months ago and he did about 4000km before this issue.

    The de cat does look like a professional job. Nicely welded piece of stainless steel pipe where the Cat was.
    https://www.google.com/search?q=cat+...hrome&ie=UTF-8

  3. #3
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    Default Re: O2 sensor downstream after decat.

    If there is no CAT you will get the error and limp mode. Regardless of if they replace it or not.
    Bring it in, let us sort out the software, problem gone forever.

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  5. #4
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Karol View Post
    Student car # 1 a 2016 Peugeot 308 1.2T threw an engine light a while back, Son took it to West Vaal Peugeot in PTA they diagnosed a faulty O2 downstream ( after the Cat) sensor and cleared the code.

    Car was fine for two weeks and the code came back, and with it the limp mode. So now we booked it it to have the O2 sensor replaced as suggested by Peugeot. ( aftermarket warranty said yes)

    However, this car has had its cat removed by the previous owner. I had my suspicions but it was confirmed that it has no catalytic converter.

    So my question is, will it not continue to throw a code with a new downstream O2 sensor because there is no Catalytic converter ? You tube tells me that the downstream O2 sensors job is to indicated if the cat is working correctly.

    Bought the 5 months ago and he did about 4000km before this issue.

    The de cat does look like a professional job. Nicely welded piece of stainless steel pipe where the Cat was.
    If it was de cated then it will occasional do this
    Best way to fix it is get someone that can just change the setting on the ECU
    Costs nothing if decent guy and changes nothing else other than the alert
    That is if the cars ECU is unlocked

    But that said if it had its cat removed then good idea to make sure the tuning is still correct
    A de-cat can cause issue with the tune that can cause problems like engine running lean
    which could cause damage
    So best to make sure all is well on that
    Last edited by Veneficus; 2024/02/23 at 02:06 PM.
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    Please remember that I think I'm funny
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    thus take 90% of what I post with 2 pinches of salt

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  7. #5
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    Default Re: O2 sensor downstream after decat.

    Thanks guys, makes sense.

    As its covered and they have already ordered the O2 sensor, I will have them replace it next Wednesday.

    Benson, I will book and send him through to your midrand branch afterwards to check the software has been done properly post decat.

    Karol Life = Σ(Choices)
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Karol View Post
    Thanks guys, makes sense.

    As its covered and they have already ordered the O2 sensor, I will have them replace it next Wednesday.

    Benson, I will book and send him through to your midrand branch afterwards to check the software has been done properly post decat.
    For R250 a Cat fooler will solve your issue, and make sure the newly replaced O2 Sensors last

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  10. #7
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Tiaan Pot View Post
    For R250 a Cat fooler will solve your issue, and make sure the newly replaced O2 Sensors last
    I saw this on your link. The picture shows the item. How does it work? It looks like it screws into the hole where the downstream O2 sensor would go, like a plug. But itís got no wire connections to communicate to the ECU ?

    im intrigued how does it fool the ecu.

    Karol Life = Σ(Choices)
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Karol View Post
    I saw this on your link. The picture shows the item. How does it work? It looks like it screws into the hole where the downstream O2 sensor would go, like a plug. But itís got no wire connections to communicate to the ECU ?

    im intrigued how does it fool the ecu.
    The cat fooler screws into where the o2 sensor would normally go and then you put the o2 sensor into that.

    In theory it will pick up less emissions and not throw a code. It's literally an adapter to fit into the o2 sensor bung and extend the o2 sensor away from the exhaust stream. There's also some steel wool in there.

    It's worth a shot at that price.

    When I bought my focus st170 it had some dodge wired thing attached to the post cat o2 sensor. Which never worked. (Was de-cat). Tried the cat fooler after disconnecting that deodorant lid resin cast thing. No difference. That being said. I wasn't going to fork out 5k for a new o2 sensor. I was fortunate enough to only have a check engine light and no limp mode.

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  13. #9
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Tiaan Pot View Post
    For R250 a Cat fooler will solve your issue, and make sure the newly replaced O2 Sensors last
    And it lasts about 3 - 6 months.

  14. #10
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    Default Re: O2 sensor downstream after decat.

    I've gone the cat fooler route a couple of times before on various vehicles, normally a bit more expensive, if i remember last time it was 1250, never had one fail or the engine light come on for that reason again.
    JK Wrangler 4.3 V8
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  15. #11
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by TheFlash657 View Post
    I've gone the cat fooler route a couple of times before on various vehicles, normally a bit more expensive, if i remember last time it was 1250, never had one fail or the engine light come on for that reason again.
    We've had two exhaust guys join forces with us, they tell a slightly different story

    But again each to his own.

    Going the software route is a proven permanent solution.

  16. #12
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    Default Re: O2 sensor downstream after decat.

    I have a Peugeot Partner van,
    Been with 2 x Peugeot Mechanics for a month
    They can not get it out of limp mode...
    What to do next

  17. #13
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Dudleytheplumber View Post
    I have a Peugeot Partner van,
    Been with 2 x Peugeot Mechanics for a month
    They can not get it out of limp mode...
    What to do next
    Where are you based?

  18. #14
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    Default Re: O2 sensor downstream after decat.

    Durban North

  19. #15
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Dudleytheplumber View Post
    Durban North
    Please get a hold of Harry at our KZN branch.
    [email protected]

    We will have a look to sort out your issue.

  20. #16
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    Default Re: O2 sensor downstream after decat.

    Peugeot 1.2 208
    Same issue as the OP.
    All sorted with hardware removal and software update. Click image for larger version. 

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  22. #17
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    Default Re: O2 sensor downstream after decat.

    We had the sensor changed two weeks ago. Son was driving back to Swaziland today and the check engine light came on just after witbank.

    will arrange to take it in to your midrand branch when he is back next week.

    Karol Life = Σ(Choices)
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  23. #18
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Karol View Post
    We had the sensor changed two weeks ago. Son was driving back to Swaziland today and the check engine light came on just after witbank.

    will arrange to take it in to your midrand branch when he is back next week.
    Oh my word! That is not good.
    But sadly we find this more and more often.
    You are welcome to contact him anytime!

  24. #19
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    Default Re: O2 sensor downstream after decat.

    Hi Benson
    Asked you about my Peugeot Partner...
    I'm in Durban North you gave me a email address...
    Do you have a phone number for your Durban guy....?

  25. #20
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    Default Re: O2 sensor downstream after decat.

    Quote Originally Posted by Dudleytheplumber View Post
    Hi Benson
    Asked you about my Peugeot Partner...
    I'm in Durban North you gave me a email address...
    Do you have a phone number for your Durban guy....?
    Sure
    Harry +27 61 507 4744

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