Is your car key fob starting to lose its range? Are you getting a 'Key Fob Battery Low' warning on your dashboard? Before you pay a dealership $50 for a service appointment, you should know that replacing a dead key fob battery is a simple 5-minute task that you can easily perform at home. In this step-by-step guide, we walk you through how to open a car key fob and replace the battery for major vehicle brands.
Tools You Will Need
- A replacement lithium button cell battery (typically **CR2032**, **CR2025**, or **CR1620** — check your old battery or owner's manual).
- A small flathead screwdriver or a sturdy coin.
- A clean, dry workspace.
Step 1: Release the Emergency Mechanical Key
Almost all modern proximity smart key fobs contain a hidden physical key blade inside. Locate the small release slider button on the back or side of the fob, slide it, and pull the metal key blade out. Set the blade aside.
Step 2: Locate the Opening Slot
Look inside the empty cavity where the key blade was slotted. You will see a small groove or indentation designed for prying. Do not insert your screwdriver into the key blade track itself, as this can damage the locking mechanism.
Step 3: Pry the Fob Apart
Insert your flathead screwdriver or a coin into the prying slot. Twist the screwdriver gently. You will hear a click as the plastic snaps holding the two halves of the fob housing release. Work your way around the edges to split the casing completely.
Step 4: Remove the Old Battery
Inside, you will see a circular lithium battery. Note which direction the positive (+) side of the battery is facing (usually the side with writing faces upward or downward). Use a plastic toothpick or a small screwdriver to gently pop the old battery out of its clip. Avoid touching the copper battery terminals to prevent bending them.
Step 5: Insert the New Battery
Slide the fresh battery into the clip in the exact same orientation as the old one. Avoid leaving fingerprints on the battery surfaces, as finger oils can increase electrical resistance.
Step 6: Snap the Fob Closed
Align the two halves of the plastic housing and squeeze them together until you hear them snap shut securely. Re-insert the mechanical emergency key blade. Test the remote buttons to confirm they light up or lock/unlock your vehicle.
Common Key Fob Batteries by Manufacturer
While you should always verify the battery size written on your old battery before purchasing a new one, here is a quick reference for common vehicle brands:
- CR2032 (Most Common): Toyota, Honda, Ford, Chevrolet, GMC, Jeep, Dodge, Nissan, Subaru, Mazda, Volkswagen.
- CR2025: Mazda smart keys, Mercedes-Benz, BMW, Audi smart fobs.
- CR1620 / CR1616: Older Honda integrated remote keys, Suzuki, Mitsubishi.