Gather the correct replacement battery for your Nissan key fob, usually a CR2032 or CR2025 coin-cell battery
Locate the seam or notch on the key fob
Use a small flathead screwdriver or a plastic pry tool to gently open the key fob
Separate the two halves of the fob carefully
Remove the old battery
Note the battery orientation, especially the positive side
Insert the new battery in the same orientation
Snap the key fob halves back together
Test the key fob buttons and remote functions
Replace the battery again if the fob still does not work properly