Code p0057?

I want to preface this by saying 2 years ago I had a code of p0161. The bank 2 sensor 2 o2 sensor was showing as the fault. Eventually I broke down and took it to the dealership, they replaced the PCM, and the problem went away. Now with the new code of p0057 it is also showing as the same o2 sensor as the issue. I have replaced both sensors on that bank and the issue is still present. I can't see any broken wires and the terminals at the PCM don't look corroded. When I tried to test the voltage with a light meter nothing came up on any of the four sensors and I had a good ground to test from. The diagnostic tool came up with an odd reading saying that the bank 2 sensor 2 was at -83 degrees after running the car for about 10 minutes. Any help would be greatly appreciated. I just don't want to take it back to the dealership and have them tell me I need to replace the PCM after only two years.

Thank you