I have an 02 Audi A4 3.0 with 103K miles on it. The CEL just came on and it shows code PO431 (catalytic efficiency below treshold, bank 2) I have done some research on this code and I've gotten different answers. Some people are saying that it's the O2 sensors and others are saying that it's the catalytic converter. I've also noticed that the car is vibrating when it's sitting and it's in gear. Any suggestions?????

 

change ur sensor first. The cat out code is p0420.