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VCDS error and limp mode

S3Powerxz Feb 3, 2018

  1. S3Powerxz

    S3Powerxz Member


    I have S3 8l AMK engine full stock except S200 filter.

    When I bought the car the rearo O2 wasn't working. I replaced it with new Bosch.

    And then I got error in VCDS:
    16804 Catalyst System; Bank 1: Efficiency Below Threshold

    Then I de-cat and put 2 straight pipes cause of the twin cat's.
    Ever since I put the new O2 sensor and got this error the car goes into limp mode.

    Clearing the DTC is the only fix. Restarting the engine doesn't work.

    Sorry for my English.
    Last edited: Feb 3, 2018
  2. Stuart B

    Stuart B Well-Known Member

    The O2 sensor needs to be mapped out, but you usually get P0420 and it didn't go into limp mode. But there is no point in having a post cat sensor with the cat removed.
  3. S3Powerxz

    S3Powerxz Member

    So why does my car goes into limp mode? There are no other errors in vcds.

    And yes it will be mapped out when i go for remap after some months.

    It's annoying to clear error codes every few days to be able to drive the car normally...out of limp mode.
  4. badger5

    badger5 www.badger5.co.uk Site Sponsor

    unless someone has blanket deleted a bunch of dtc's it should have thrown a code if its unhappy enough to limp mode
    (if you are getting limp mode and not something else)
  5. S3Powerxz

    S3Powerxz Member

    Well when the error came up the turbo is making only 0.3 bar of boost. As far as i know this is called limp mode.
    Clearing the error with vcds fix the things until error show up again.

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