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P0421 Diagnostic Trouble Code Discussion for April 2008

Warmup Catalyst Efficiency Low (Bank 1)

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Trouble Ticket Help Requests for DTC P0421
Help Request Posted
2001 Audi A6 Quattro 2.7L MIL Lamp on VIN: WAUED64B01
P0421: cat not operating efficiently sporadic DTC. The cats on this car are not damaged and appear to be working ok...Is there an Audi tech who has heard of a Service Bulletin that corrects this problen with a software upgrade to the ECM? We understand that that Basically this means that the oxygen sensor down...
April 16, 2008