One problem related to o2 sensor has been reported for the 2002 Audi A4. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2002 Audi A4 based on all problems reported for the 2002 A4.
The ignition coil made the vehicle ride rough. While driving, the vehicle lost power and cut off. The dealer stated they would only replace 1 out of 6 coils. The service technician had driven the vehicle five miles and the a second coil failed. Audi replaced all six coils then the remaining five were "j" coils. The engine warning light had come on. The vehicle had been serviced repeatedly by father's & sons, but they had not completed the repair. All of the oxygen sensors and the catalytic converter had been replaced. (some twice) the other emission parts were replaced. The service dealer did not give the consumer the paper work because Audi did not pay the full cost for repairs. The vehicle was still under warranty.