Hey guys, so my 06 had about 245k miles on the cluster. I had the dealership agree to fix the catalytic efficiency code before I bought it. The shop replaced both cats and all 4 o2 sensors. Then about a month ago it threw another cat efficiency code so I took it back. They said they replaced a bad o2 sensor and reset the code. Then two weeks ago it came back. They replaced another o2 sensor but also asked me if I was aware that my xterra had a frontier pcm in it. Then last week the code came back again...they took it in (claimed to fix another o2 sensor) and reset the code again. I picked it up and the code came right back after one drive cycle. Could the frontier pcm be blowing o2 sensors or throwing false codes? Or is the shop just trying to get out of more free work?