Where is bank 1, sensor 2, O2 sensor located on 1996 Audi A4?

[lilkhmerraider]

My car had a recent check engine light and my mechanic diagnosed the computer of my car and a P0136 code is coming up. The O2 sensor located in bank 1, sensor 2 needs to be replaced. I can change it myself but I have no idea which one it is, because there are 2 near the cat converter. Any pictures or explanations will help. I just want to know which one it is. And which O2 sensor should I get? Right downstream, left downstream? Any info?

 

[StraightShooter]

Sensor 1 is between the engine and the converter, Sensor 2 is in, or just after the converter. Bank 1 is on the same side as cylinder 1 if its a v-engine, (if you have an inline 4 or 6, there's only one bank of cylinders).
I'm not 100% familiar with Audi's but, my suggestion is to replace both left and right bank sensors at the same time, (if there are two). The engine runs with all cylinders and the computer makes air/fuel corrections based on ALL available sensor data, so it needs to "sense" ALL the exhaust.
Now, if there actually is two downstream sensors, and if you replace only one sensor, the computer will detect one (brand new) correctly working sensor and one slower working sensor, and set a code for the other side.
It's the same advise for replacing 2 tires, or 2 brake rotors. Why would you do just one?