I have a 2000 maxima, replaced the mass airflow sensor due to rough idle condition. Since then, replaced the rear o2 sensor and as part of that repair, my mechanic had to have the nissan dealer reboot or put a software patch on the engine control module as part of the rear o2 replacement. The dealer charged $99 for that.
My mechanic found a rich running condition before I picked up the car. He removed the idle air control and cleaned that, and removed the engine control module, and discovered evidence of a fire within it. Somehow, the car ran fine inspite of a that failure within the ECM.