Toyota Sienna key fob battery

Separate remote fob

1. This remote is its own fob, separate from the metal key, which makes it one of the easier ones to open.
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. Swap the cell or cells, keeping the same side up as the old ones.
4. Reassemble and test from a short distance.

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.

Smart key (push-button start)

1. Start by freeing the hidden metal key: there is a latch or slide on the case, and the blade comes out once it moves.
2. Use the slot where the metal key sat. Twist, do not lever hard, and work along the seam until the halves separate.
3. Note which side of the old coin cell faces up (usually the side with the writing), lift it out with a plastic tool, and press the new one in the same way.
4. Reassemble, refit the emergency key, and check that the car sees the fob when you press 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.

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.