Oxygen Sensor on Series 1

I understand where the sensor is on the rear exhaust manifold. Problem is, I can't see the thing from any angle at all. How do I reach/figure out exactly where it is? Any help is greatly appreciated.

It is located behind the rear cylinder head. move the wires out of the way and you'll see it.

Yep. If you get on your knees in the engine bay, you need to shove your head as far back as possible to get a good view between the bulkhead and the engine. You really can't miss it once you find it.

Thanks for all the help guys. I got it in without much problem, just had to really reach for it though. My check engine light is still on with code P171 which the dealer book explicitly states is oxygen sensor. Any ideas?