I added another Nissan to my fleet. I bought a 2010 Murano and the guy said that it had a bad transmission. I got a good price and I have a parts Murano with a good trans. Before I trade out the trans I decided to check it over and change the filter and fluid. I haven’t changed the external filter. The internal filter was completely covered. I cleaned it with brake cleaner and put it back together. It drove fine and sounded way better. After a bit, it couldn’t move. I pulled it back in and took the trans pan and the filter was clogged again. It was also shows a pending code for the Stepper motor(P1778). I bought a new motor and filter and replaced them both.

I took it on a short drive and it worked fine then it seemed like it was stuck in a lower gear. The code is still present. I found some info in the FSM about the relearning process. Should I try that? Or is there anything else that I am missing before I give up and switch the trans?

There's no way any CVT should have that much crud in it. I think it's trying to tell you something.