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What Can Cause a Lambda Sensor To Go Bad ?

Discussion in 'A3/S3 Forum (8L Chassis)' started by A3 T, Jul 15, 2013.

  1. A3 T

    A3 T Lord Of The Rings

    Feb 23, 2011
    Likes Received:
    I changed the sensor about 3 months ago because i kept getting this error:

    16804 - Catalyst System: Bank 1: Efficiency Below Threshold
    P0420 - 35-10 - - - Intermittent

    After changing the sensor I've not been getting the error and the car has felt really good.

    I've noticed the car has felt not right over the last couple of days so i gave it a quick scan and the error has come back.

    I remember reading a thread a while back titled something like “why does my car keep eating lambda sensors” but i can find it now.

    So any ideas what could be causing them to go bad?
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  3. <tuffty/>

    <tuffty/> Badger 5 Edition...Its all about the flow...
    Staff Member Moderator Audi S3

    Sep 14, 2008
    Likes Received:
    Sounds like a faulty CAT not a faulty sensor...

    16804/P0420/001056 - Ross-Tech Wiki
    16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold
    Possible Causes

    Leakage in Intake and/or Exhaust System
    Catalyst faulty
    Oxygen Sensor(s) faulty
    Oxygen Sensor(s) Control faulty

    Possible Solutions

    Check Intake and Exhaust System for Leaks
    Check Catalyst
    Check Oxygen Sensor(s)
    Check Oxygen Sensor(s) Control
    Perform Oxygen Sensor(s) Aging Check

    Special Notes

    For 1.8T's experiencing this fault code, this thread may be useful VWVortex.com - Aftermarket DP/Cat -DTC - Cat efficiency below threshold - Who has this DTC and wich DP/Cat


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