Fault Code P0431
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Joined: Mar 2007
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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.
Club AutoUnion
Joined: Mar 2000
Posts: 31,629
Likes: 49
From: Fort Collins Colorado
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
APR and other tuners can turn this off with their flash on the other Audis
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