>> A << Battery Installation
WARNING: This page is about a different car, the 2008 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
Do not allow water or dust to enter the inside of the transmitter assembly when it is open. Also, do not touch the precision electronic device.
Install a new battery with the positive side facing toward the lower cover.
Replacement battery: Coin-type lithium battery CR2032