Infiniti FX45 key fob battery

Smart key (push-button start)

1. Most push-button fobs hide a metal backup key. Press or slide its catch and draw the key out first.
2. Look inside the empty key slot for a notch. Put the tip of the metal key or a small flat screwdriver wrapped in tape there and twist gently until the shell splits.
3. Pop the old battery out with a toothpick or plastic pick, not a metal blade, and seat the new one with the + side matching the old one.
4. Close the case until it clicks all the way round, put the metal key back, then try the buttons and a push-button start.

Infiniti Intelligent Keys normally hold a mechanical key behind a release knob; the slot behind it is where you pry.

A CR2025 is 20 mm across and 2.5 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.

Separate remote fob

1. A separate fob has no key blade inside, so it opens with nothing but a coin or a small screwdriver.
2. Look for a screw on the back or a notch on the edge. Remove the screw if present, then twist a coin in the notch to split the case.
3. Replace the cell, keeping the + side where it was, and check the small metal tab still touches it.
4. Close the fob and test it. If it does not work, open it again and check the cell is seated flat.

A CR2025 is 20 mm across and 2.5 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.