1. Locate the key release button on the side of the key. It is usually a small, round button with the BMW logo.
2. Press and hold the key release button while pulling on the key. The key should come out of the housing.
3. Use a small flat-head screwdriver or other prying tool to gently pry open the key housing. Be careful not to damage the housing or the key.
4. Once the key housing is open, you will see the battery inside. It is usually a small, round, silver battery.
5. Remove the old battery and insert the new battery, making sure to match the positive (+) and negative (-) terminals.
6. Snap the key housing back together.
7. Insert the key back into the car and test it to make sure it works properly.
