What is the best answer to fix the Code# P0421 for Audi 2000 A6?

I just bought to Audi 2000 A6 Quattro, It had the check engine light on. AutoZone and Mechnic Shop ran the diagnostic for error code are:

1. (Bank 1, sensor 2) and (Bank 2, sensor 2) are bad

2. catalyst efficiency low-bank 1

3. the oxygen sensor monitor the catalytic converters ability to store oxygen

4. catalytic converter defective (failure possibly probable causes)

5. Catalytic converter defective (failure possibly due to #2, 3, or 4)

6. Engine misfire or running condition

7. Large vacuum leak

8. Engine oil leakage into exhaust-valve guide seals, piston rings.



Can someone have any ideas to know exactly how? I would like to know what's specific error for my problem, so I would save money and time to fix my car? Thanks. God bless you!What is the best answer to fix the Code# P0421 for Audi 2000 A6?You need a new catalytic converter....that is what that code meansWhat is the best answer to fix the Code# P0421 for Audi 2000 A6?Agree with Bob sleigh you have defective catalytic convertersWhat is the best answer to fix the Code# P0421 for Audi 2000 A6?cat coverter efficincy low. check at the dealer there is a ECM reflash to correct false cat efficincy faults if none are available you will need to replace the fail cat converter