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Fault Code P0431

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Old 08-16-2007, 09:44 AM
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Default Fault Code P0431

I find that about once per month I get the check engine light and the following emission related fault code - P0431 Warm Up Catalyst - Efficiency Below Threshold. I assume that this may be related to the after-market cats on my Milltek down pipes and that the code is more of a nuisance than a real concern (until I am due for the State emissions test, perhaps). Anyone out there with similar experiences or greater wisdom, please chime in.
Old 08-16-2007, 10:00 AM
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Default Yep - the ECU looks at the O2 sensor before and after - It is expecting to see a flat line

on the sensor after the cat and fluctuation on the one before - if the two track each other then it suspects a failing cat.

APR and other tuners can turn this off with their flash on the other Audis
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