O2 sensor location

[rzafreak]

Hi all. I've had my e71 50i for a little over a year and just started getting a CEL referencing Bank 1 Sensor 2. I get that Bank 1 is the (US) passenger side, and I get that Sensor 2 refers to the downstream sensor as opposed to the pre-cat sensor. I've attached a pic of Bank 2 for reference. Sorry for the noob question but is Sensor 2 the one on the top (red circle) or the side (green circle)? Or is it in a totally different location? If anyone has part numbers available, that would be a great help as well. Thanks in advance!

[Colodano]

Pretty basic, follow your exhaust flow from the turbo down.... Sensor #1 is pre-cat and upstream, sensor #2 is post-cat, or downstream. Aka. red is #1 green is #2.

[StatenEye]

Originally Posted by rzafreak

Hi all. I've had my e71 50i for a little over a year and just started getting a CEL referencing Bank 1 Sensor 2. I get that Bank 1 is the (US) passenger side, and I get that Sensor 2 refers to the downstream sensor as opposed to the pre-cat sensor. I've attached a pic of Bank 2 for reference. Sorry for the noob question but is Sensor 2 the one on the top (red circle) or the side (green circle)? Or is it in a totally different location? If anyone has part numbers available, that would be a great help as well. Thanks in advance!

Bottom of the heat shield, there will be the downstream sensors on the outer side of each of the downpipes. The cat is about 9 inches long, like my dong. You take the clip off, and then the sealing material and its pretty easy to take the sensor off from that point. Hand thread the new one on and make sure you don't cross thread. Should take like 30 mins I guess.