Question

Where is the oxygen sensor bank 1 sensor 2 located on a 2003 Cadillac DeVille?

Answer 1

bank 1 is always the side of the engine  that has cylinder #1. you can tell by looking for the most forward cylinder. line up the sparkplugs . whichever side is most forward, this is cylinder #1 which would also be bank 1 then the other side would be bank 2...sensor 1 is always pre converter, sensor 2 is always after converter