Emissions question...

[BigMac76]

Ok so driving the car here lately, even after the plug change, I've been noticing the car is running a bit on the rich side. Noticed some black on the back of the car and the smell of the exhaust, as much as I love it, is the main indicators. Also noticed that every so often sitting at a light, it will idle a bit on the rough side. So I hooked up the scanner and noticed that it's throwing a P0161 and it's pending as well. It's the O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 2, post cat O2 sensor.

Now I know the pre-cat o2 sensors can create a lean or rich condition as well as "limp mode" rich. Now will/can the post-cat sensors do the same and cause the same condition creating my symptoms?