The Lexus GS300 remote uses a Lithium-coin battery, as do most other automotive keyless-entry remotes. The GS300's remote is integrated with the key, but it does not impede the battery replacement procedure. Replacing the Lexus GS300's keyless-entry battery is a five minute job as long as you have the correct tools. The replacement battery costs less than $5 at most online retailers, including Amazon.com and Battery Mart. You should also be able to pick up a new battery at an electronics store.
Gather the tools, battery and remote, and bring them to a flat work area. Turn the Lexus remote over with the buttons facing down.
Remove the small Phillips screw from the rear of the remote. Then insert the flat head screwdriver in between the key and the plastic edge of the remote. Gently push up to pop the top half of the device off.
Grasp the keyless-remote module and remove it from the case. Remove the two Phillips screws from the keyless-remote module.
Open the module to find the battery. Remove the discharged battery and place the new battery into its place. Use the markings (positive or negative) as a guide for placement.
Snap the module back together and tighten its screws. Re-insert it into the remote case, and then re-attach each half of the remote case. Replace the small Phillips screw.
