Cadillac Repair: catera o2 sensors, o2 sensors, catera

Question
A friend put my 97 catera on his computer diagnostic reader it read the #2 sensor was bad but there are 4 witch one is the number 2

Answer
The one closest to the radiator.

What CODE did you get as there are sensors located at:

Bank 1 sensor 1.  
Bank 2 sensor 1.  
Bank 1 sensor 2.  
Bank 2 sensor 2.

Sensor 2 is usually the front exhaust sensor on the passengers side. BUT, If I had the CODE, I could tell you exactly.