Does any one know which o2 sensor that is? PO161 Where is the cheapest place to find o2 sensors?
That would be the O2 sensor after the catalytic converter on the passenger side.
I can't direct you where you'll find it the cheapest except suggest finding out what part number you need and searching the autoparts stores and possibly on eBay. You'll most likely pay more at the dealer for a replacement part but you should replace it with the same OEM part (ACDelco or Bosch) if you buy it anywhere else. I'd stay away from other generic brands.
Here's some more info to consider at this link. Your problem could be more than just replacing the sensor.
Hey OP I too jus got this code on my 96 Z71. It states that it is Bank 2 Sensor 2, but I as well am not too sure which one of the 4 sensors this would be. From what I've searched on this site so far, even it being a little bit more of an expensive route, it is HIGHLY recommended that you go OEM with your O2 sensor. A lot of guys on here swear by them and have stated that they have problems with Bosch and other aftermarket brands. Problems that I read stated that the code was still there after they replaced the sensor and would not go away. GL :)