Cadillac CT5 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. Use the slot where the metal key sat. Twist, do not lever hard, and work along the seam until the halves separate.
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. Snap the halves back together, slide the metal key home, and press each button, then try the start button from the driver's seat.

Cadillac smart remotes commonly hide a key behind a side button. With it out, the case opens at the bottom slot.

A CR2450 is 24.5 mm across and 5.0 mm thick, much fatter than a CR2032. A thinner cell will rattle and lose contact, so buy the exact size.

Separate remote fob

1. The remote is a small standalone unit. You will not need to touch the ignition key at all.
2. Turn it over: some older fobs use one small screw, newer ones just clip. Pry at the seam once any screw is out.
3. Lift the old coin cell out and press the new one in with matching orientation.
4. Close the fob and test it. If it does not work, open it again and check the cell is seated flat.

A CR2450 is 24.5 mm across and 5.0 mm thick, much fatter than a CR2032. A thinner cell will rattle and lose contact, so buy the exact size.