Where is the speed sensor b input located on Nissan versa note sv 2015 ?

For this diagnostic trouble code, there is a full test procedure to go through that will help narrow down the cause of the code fault. I would suggest obtaining a shop manual or getting assistance to troubleshoot this. The secondary speed sensor is located directly opposite the primary, on the back side of the housing, compared to the front side for the primary. For CVT's, I find most concerns to be internal and not serviceable. But good luck, hoping yours is not like this!