I have a 2003 CTS 3.2 thats showing codes - P0160 - O2 sensor circuit no activity (bank 2 sensor 2) and - P0161 - O2 sensor heater circuit malfunction (bank 2 sensor 2).
After a lot of searching, I'm noticing multiple threads where people with the same 2 codes will change out the drivers side post-cat sensor (or even all 4 at times) and still have the same codes. The problem is that none of the OPs post up a solution in any of the threads.
A few posts had mentions of checking the wiring, which was my first thought when I ran the codes. I went under the car to check all of the connections and I found a good amount of oil dripping from around the O2 connectors (rear main seal?) All of the visible wiring seemed to be OK. I unplugged the drivers side sensor and there was some oil in the connector itself that I cleaned out. While I had it unplugged, I started the car and let it run for a few minutes and pulled the codes again to be sure that the drives side was the affected circuit. I got the same 2 codes, plus one additional pertaining to bank 2 sensor 2.
So now what? My next thought would be to test the wiring from the O2 sensor to the ECM. I own a decent voltmeter, but I have no idea how to use it.
Maybe someone out there has solved this problem or has seen it before and can offer me some sort of direction. The car is due for inspection on Monday and will fail emissions with these codes present.