Toyota Tundra 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. Find the slot along the edge and turn a coin in it. Go slowly so the clips do not snap.
3. Swap the cell or cells, keeping the same side up as the old ones.
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.

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.

Key with remote in the head

1. This type has the buttons built into the key head. The cell is inside that head, between two clipped halves.
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. Press the head together until it clicks and test the buttons. The transponder chip that lets the car start is separate from the battery, so starting should not change.

A CR2016 is 20 mm across and 1.6 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. Before you take the old cell out, look at its face. Put the new cell in with the same side showing, and avoid touching both faces at once.
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.