Eric 2.7

I had a bank 2 O2 sensor 1 going out and throwing a code, so I decided to go ahead and replace it. Was not really a bad DIY job taking less than 1 1/2 hour with me taking my time and making sure to do everything right. The most time consuming thing is taking things out of the way and removing the old cabling and routing the new sensor wiring correctly. Location of the bank 2 (driver side) primary sensor was a little intimidating at first since you really have to work to just see it, but once everything is out of the way, it is quite accessible. The bank 1 sensor is quite a bit easier to see and reach.

Couple of notes.
1) I used a Lisle 02 sensor socket from sears. I normally hate Lisle stuff, but this one had a nice groove, although it needed to be deburred so as to not cut the 02 sensor flex relief.
2) I bought the OEM sensor with the plug n play connector ($140), but next time I'd go for the Bosch universal at $63 which comes with a very nice splice kit and would only take a little more time to do.
3) I only let the car sit for like 30 minutes before doing the job, but that was enough time for the exhaust header to cool, but it is a good idea to do this on a cool header.
4) I used 18" of extensions with a U-joint on the socket and an 18" breaker bar and the old 02 sensor came right out.
5) On the 2.7 motor it really helps to remove the Y-pipe and the hose from the secondary air injection pump to the combi valves (Tip).

Peccavis

I used the Bosch universal in my old A4, and it worked fine. Haven't had the need on the 2.7T (yet). I know nobody wants to cut wires, but it was very simple to do, and saved what... $70 or more? Hey, it worked.