Well for me the answer was to get a new gas cap.
I am one of the lucky ones. My second Maxima-45k miles on this one, 5 years old.
I have heard of people changing oxygen sensors, mass air flow sensors (whatever that is), getting catalytic work, coils changed and on and on and the light still comes on.
My friend had the same problem on a Taurus and it was a vacuum leak and was fixed for about $45 by a non-dealer.
Nissan flat out told me (Parts, not service) that if the car shows no changes in drive-ability, knocking, rough idle, rough driving, loss of acceleration, and passes smog tests--then perhaps forget about it.
I have read a lot of posts where people spent $800-$2000 and the light is still on and Nissan offers no remediation, refunds, or apology.
So try a new gas cap first. Mine cost $7 from Pep Boys. I know I am one of the lucky ones.
Patty