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Q: check engine light on 2004 Audi Allroad Quattro

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check engine light is on......scan shows 2 codes P0421 and P2197. replaced air filter today. praying it is not cat. converter(s).aceleration is perfect and I detect no foul odor from engine or emissions.Allroad did sit for 5-6 weeks and has 146K on it. Has been dealer maintained since new. Still runs perfectly Anyone have thoughts? Thank you all!
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The P0421 is a catalytic converter related code all right, P2197 says an O2 sensor is stuck lean, fixing that code first may solve your problem because if the computer does not see a good balanced relationship between the O2 sensors it then assumes the cat is bad. Perhaps it is lean for a reason any way proper diagnosis is needed before replacing parts and use of a good professional grade scan tool may get to the root of the problem quickest.
Thanks very much Patrick. Think I'm gonna have Audi dealer do the scan. Don't believe the cat. con. is gone..........runs too well......perfectly, actually!

Thanks again Patrick!
An O2 sensor can cause a false cat code. There is a procedure called "generating readiness" that will be required to detrermine O2 or Cat. If the Cat converter is marginal you would never know except for the chcekc engine light coming on. If the dealer determines that the O2 senswor is the problem, I would recommend replacing all four.
Thanks very much AA&TW. If it is cat. con. is there a less expensive route to take than Audi dealer? Is the part available other than Audi dealer?

If your intention is to keep the car, then no. We have installed aftermarket converters of all kinds, even ones that claim California compliant, they do not work for long if at all. Audi is the only version I would recommend. They are expensive so before you decide to fix the car, make sure you like the car. At 145k, your into the money years.
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