that is the response i got when with my ecu diagnostic. what do i do now as far as fixing this problem?

 

The rear O2 sensor is used only to monitor the condition of the main catalyst... and won't affect your gas mileage.

Try resetting the ECU and see if the problem persists.

There's supposed to be a service bulletin for the 95-96 Maxima O2 sensors and word has it that they may replace it free of charge if you bring it in...

Do a SEARCH on O2 sensors (or other keywords) to find the thread.