Key Fob Battery Replacement Guide: Every Brand, Step by Step

Most key fobs use a standard coin cell battery—CR2032, CR2025, or CR1632 are the three you’ll run into. You can replace it yourself in about five minutes with a small flathead screwdriver or a plastic pry tool. You just need the correct replacement battery, a steady hand, and the right opening method for your specific brand. Here’s how to do it for every major brand, from Subaru to BMW, without cracking the case.

What Battery Your Fob Needs

Check your owner’s manual first. If you don’t have it, pop the fob open (see opening tips below) and read the number printed on the old battery. Below are the most common types used across popular brands:

Why the exact type matters: CR2032 and CR2025 are both 20 mm in diameter but different thicknesses. The CR2032 is 3.2 mm thick; the CR2025 is only 2.5 mm. A CR2025 may rattle or lose contact, and a CR2032 may not fit in a CR2025 slot. Don’t swap them.

Additional battery dimensions if you encounter something else: CR1632 is 16 mm diameter and 3.2 mm thick (used in some older Nissan and certain Mitsubishi fobs). CR2450 is 24.5 mm diameter and 5.0 mm thick (used in a few larger fobs like some GM models). Check the number on the battery itself.

Before You Start: What You'll Need

• Replacement battery – exact type printed on the old battery
• Small flathead screwdriver or plastic pry tool (a spudger or guitar pick works)
• Electrical tape (optional) – wrap the tip of a metal screwdriver to prevent scratching
• Owner’s manual (helpful for model-specific release button locations if you get stuck)

First step: Take a photo of the open fob before removing the battery. That way you won’t guess at the orientation later.

How to Open a Key Fob Without Breaking It

The general process is the same across most brands, but the exact seam or slot location varies. Here’s what to look for:

1. Remove the mechanical key first. Almost every modern fob has a release button or slide latch. Press it and pull the emergency key out. This often exposes a notch or slot for prying.
2. Look for the seam. With the key removed, examine the fob’s edge. There’s usually a thin line where the two plastic halves meet. Some fobs have a small notch at the top near the key ring.
3. Insert your tool at the notch. Place the flat tip into the notch and gently twist. If the fob doesn’t budge, work the tool around the perimeter—don’t force one spot. Prying only at the notch can crack the housing.
4. Separate the halves. Once the inner clips release, pull the two halves apart by hand.

Where people get stuck: If you can’t find a notch, check for a hidden release button under the keyring loop or along the side edge. Some VW and Audi fobs have a slot on the side opposite the key blade, not near the keyring. If you still can’t find it, check your owner’s manual before forcing anything—some fobs are not meant to be opened (see “When to Go to a Dealer Instead”).

Brand-by-Brand Opening and Replacement Steps

Subaru

Battery: CR2032

Opening method (2010–2020 models – Impreza, Outback, Forester): Press the small release button on the back and slide out the mechanical key. You’ll see a notch at the base of the key slot. Insert a flat tool there and twist gently to pry the two halves apart.

Step by step:

1. Slide out the mechanical key.
2. Insert a flat tool into the notch at the key slot and pry the case open.
3. Lift the circuit board slightly from the battery side – it’s loose.
4. Slide the CR2032 out of the holder (it’s clipped in).
5. Install the new battery with the (+) side facing up (check your photo to confirm).
6. Snap the halves back together and reinsert the key.

Branch: If the fob doesn’t snap back together easily, check that the battery is fully seated and no wires are pinched. Do not force the halves—remove and re-seat the battery.

Ford

Battery: CR2032 (most models – F-150, Escape, Explorer 2015+)

Opening method: Ford fobs have a seam around the edge. For integrated key fobs (with a flip-out key), there’s usually a slot near the keyring. For separate fobs (like the F-150’s rectangular fob), press the release button, remove the emergency key, and look for the notch at the key slot.

Step by step:

1. Press the release button and remove the emergency key (if present).
2. Locate the small notch – often near the keyring hole or at the seam.
3. Insert a pry tool and twist to pop the fob apart.
4. Pry the battery out using a tool (do not bend the metal contacts).
5. Insert the new CR2032, (+) side facing up.
6. Align the two halves and press firmly until they click.

Honda

Battery: CR2032 (Civic, Accord, CR-V – most years)

Opening method: Honda fobs are tightly sealed. There’s a small slot at the top near the keyring. Some models require removing the mechanical key first via a release button on the back.

Step by step:

1. If your fob has a release button, slide the key out.
2. Insert a thin flat tool into the slot at the seam.
3. Pry the fob open – it may be tight. Use gentle twisting along the edge.
4. Push the battery out from one side (use a non-metal tool to avoid shorting the contacts).
5. Install the new battery, positive side up.
6. Press the halves together until they snap shut.

Where people get stuck: Honda fobs are notoriously hard to open. If you can’t get the halves apart, don’t use excessive force with a metal screwdriver—you’ll scratch the plastic. Try a plastic pry tool inserted deeper along the seam. A thin guitar pick can work.

Toyota & Lexus

Battery: CR2032 (Camry, RAV4, Corolla; Lexus RX, ES)

Opening method: Slide the release latch and pull out the emergency key. The notch is inside the key opening, usually at the bottom edge. Insert a small flathead there.

Step by step:

1. Slide the release latch and pull out the emergency key.
2. Insert a small flathead screwdriver into the notch exposed by the key.
3. Gently pry the case open – work around the edge if needed.
4. Remove the old battery – it usually slides out from under a metal clip.
5. Install the new CR2032 with (+) facing up.
6. Snap the case back together and reinsert the key.

Branch: If the fob still doesn’t respond after the battery swap, try holding the fob directly against the start button. Some Toyota push-to-start systems enter a backup detection mode if the fob signal is weak. If it works that way but not from your pocket, the fob may have internal damage or the battery contact needs bending slightly.

BMW

Battery: CR2032 (standard non-display fobs for 3 Series, 5 Series, X3 from the 2010s)

Opening method: Press the small button on the side to release the emergency key. After removal, look for a seam along the side – not where the key was. Pry open along that seam.

Important: The BMW display key (with a small screen, used on some newer models) has a non-replaceable rechargeable battery. Do not attempt to open it. If the battery fails, the dealer must replace the entire fob.

Step by step (standard fob):

1. Press the button on the side and pull out the emergency key.
2. Locate the seam – often on the opposite side from the key slot.
3. Insert a pry tool and separate the two halves.
4. Carefully lift the battery out. It may be glued or held by a clip.
5. Insert a fresh CR2032, positive side up.
6. Align the halves and press together until they click.

After replacement: Some BMW comfort access fobs need a short resync: get in the car, press the start button with the fob, and the car should detect it within a few seconds. If it doesn’t, hold the fob against the steering column where the key icon is located.

Hyundai & Kia

Battery: CR2032 (Elantra, Sonata, Tucson; Optima, Sportage, Sorento – 2011+)

Opening method: Press the small button on the back to slide out the emergency key. Inside the key opening, there’s a narrow slot. Insert a flat tool there and twist.

Step by step:

1. Press the button and remove the emergency key.
2. Find the slot inside the key opening.
3. Insert a flat tool and twist to split the fob.
4. Gently pry up the battery – it’s often held by a spring clip.
5. Insert new CR2032 with (+) facing up.
6. Snap the fob closed and slide the key back in.

Nissan

Battery: CR2025 (verify – Altima, Rogue; some newer models use CR2032)

Opening method: Slide the latch and remove the mechanical key. Use a small screwdriver on the seam along the edge.

Step by step:

1. Slide the latch and pull out the mechanical key.
2. Insert a flat tool into the slot inside the key opening or along the seam.
3. Gently twist to separate the halves – they may snap apart.
4. Lift the old battery out; it sits under a retaining clip.
5. Install the new CR2025 (or CR2032 if that’s what you removed) with (+) facing up.
6. Press the halves together until they click and reinsert the mechanical key.

Chevrolet / GM

Battery: CR2032 (Malibu, Equinox, Silverado keyless fobs)

Opening method: Most GM fobs have a small slot on the side or near the keyring. Remove the emergency key first (slide the release latch) and look for the notch inside the key opening.

Step by step:

1. Slide the release latch and pull out the emergency key.
2. Locate the notch inside the key opening or along the seam.
3. Insert a flat tool and pry the fob open.
4. Push the old battery out from one side – avoid bending the metal contacts.
5. Insert the new CR2032 with (+) facing up.
6. Snap the fob closed and reinsert the key.

Where people get stuck: Some GM fobs have a hidden screw under a sticker or behind the keyring loop. If prying doesn’t work, check for a small screw before applying force.

Volkswagen & Audi

Battery: CR2032 (most keyless fobs)

Opening method: VW/Audi fobs often have a slot on the side opposite the key blade, not near the keyring. Remove the mechanical key first (press the release button) and look for a seam or slot along the fob’s edge.

Step by step:

1. Press the release button and pull out the mechanical key.
2. Look for a small slot on the side of the fob (not inside the key opening).
3. Insert a flat tool and gently pry the two halves apart.
4. Remove the old battery – it may be tucked under a plastic tab.
5. Insert the new CR2032 with (+) facing up.
6. Align the halves and press together until they snap closed.

After replacement: Most VW/Audi fobs resync automatically when you start the car. If not, press the lock button a few times near the ignition.

After the Battery Change: What to Do Next

Most fobs work immediately after the battery swap. Here’s how to confirm:

• Press any button on the fob. The LED should flash. If it doesn’t, the battery may be installed upside down or the contact needs a slight bend.
• Test all functions: lock, unlock, trunk release, and panic. If only one button fails, the fob may have a different issue (broken switch or internal damage).
• Try starting the car. For push-to-start vehicles, press the start button with the fob in your pocket or on the console. If the car doesn’t recognize it, hold the fob directly against the start button or the steering column (check your manual for the backup location).

Multimeter check (optional): If the fob still doesn’t work, measure the old battery voltage. A healthy coin cell reads about 3.0 – 3.2 V. Below 2.8 V is dead. This confirms the issue was the battery and not something else in the fob.

When to Go to a Dealer Instead

Some fobs cannot be opened without breaking them, or they require specialized programming. Take the car to a dealer or a professional automotive locksmith if any of the following applies:

• The fob is a sealed, non-serviceable unit – examples include the BMW display key, certain Mercedes comfort-access fobs (with chrome buttons), and some recent GM fobs with no visible seam. Forcing them open can destroy the fob.
• The battery is soldered in – a few premium fobs (e.g., some Audi advanced key fobs) use a soldered coin cell. Replacing it requires desoldering and is best left to a repair shop.
• The fob needs programming after a battery change. While most cars resync automatically, some models (especially older GM, Chrysler, or aftermarket remote starts) require a specific sequence to reconnect the fob to the car. If the car doesn’t recognize the fob after a new battery, the dealer or a locksmith with diagnostic equipment can handle it.
• The fob is physically damaged – cracks, broken buttons, or missing clips. A battery swap won’t fix internal damage, and the fob may need replacement.

If you’ve followed the steps and the fob still doesn’t work after a fresh battery, a dealer visit is the safest next step. They can test the fob, reprogram it, or confirm whether the transponder chip or circuit board has failed.