A6 with possible cat problems

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04-09-2012, 07:53 AM

#21

ezveedub

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Quote:

Originally Posted by johnkk

I don't think it's the Cats. Have any O2 sensors ever been replaced? I'm still thinking downstream O2 sensors.

Have you given the Cats a whack to see if they rattle and are starting to fall apart? Also, check the Flex pipe ahead of the Cats for leaks.

You get a different DTC fault for an upstream air leak in the exhaust or flexpipe. Unless you have an O2 sensor DTC or other related DTCs also, the cats are usually the issue AFAIK.