I have a 2001 outback and need to change the downstream o2 sensor, but I can't find it.  I think I found the upstream one.  Is there a thread with pictures or can someone describe where it is.  I not a novice mechanic but I just can't find the darn thing.

Thanks for the diagram but it does not match what is going on under my car.  I had seen this one which is why I was looking toward the middle of the exhaust for the downstream sensor.  And that is why I could not find it , it is not there.  Turns out both the up stream and down stream are toward the front of the exhaust system and very close together.  You can see where they both plug in right next to each other in the engine compartment.  Now that I have located it and it looks like it won't be too bad to get out,  I'm thinking about trying the cheat fix using a plug anti fouling extension with the sensor to prevent the P0420 code from occurring.  Anyone have any luck with that and tips for doing it.