Toyota C-HR key fob battery

Key with remote in the head

1. The remote electronics sit in the plastic head of the key itself, so there is no separate fob to open.
2. Many key heads split along the side seam. Start at the small notch and pry a little at a time.
3. Inside you may find a small circuit board in a tray. Lift the board out if the cell is underneath, swap the cell with the same side up, and refit the board.
4. Snap it closed and press each button. The car still starts with a dead remote battery on most of these keys, because the start chip needs no battery.

A CR1620 is 16 mm across and 2.0 mm thick. It is easy to confuse with the 20 mm CR20xx sizes, which will not fit.

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.

On most Toyota smart keys the metal key slides out after you press a small release, and the case opens at the slot it leaves behind.

A CR2032 is 20 mm across and 3.2 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.