Replace the Key Fob Battery

When the key for a Subaru Impreza (fifth generation, GK/GT, 2017–present) starts working only from a hand’s width away, or the dashboard pops up an “Access key battery low” note, the coin cell in the fob is on its way out. This is the first Impreza on Subaru’s Global Platform, sold as both a hatchback and a saloon, and higher trims carry the Keyless Access smart fob with push-button start — the slim remote with lock, unlock and boot buttons and a mechanical blade clipped inside. Renewing that cell is quick and needs nothing more than a small screwdriver. Here is the precise battery, the way to open the fob without scratching it, and why a genuinely new key still has to go through a dealer.

How to Tell the Fob Battery Is Dying

• Its range keeps shrinking. You find yourself standing over the door handle to lock or unlock — the earliest sign, and the most dependable.
• “Access key battery low” on the display. The Impreza spells this out in the instrument cluster when the smart fob’s cell weakens; don’t put off acting on it.
• Push-button start goes intermittent. If the car will only start when the fob is held right against the button, the transmitter is low on power.
• Cold snaps make it worse. A near-flat lithium cell drops voltage in the cold, so the fob misbehaves on icy mornings and steadies up once things warm.

A Keyless Access cell tends to give two to four years of service. If yours is around that age and doing any of the above, swap the battery before you suspect the aerials or the immobiliser.

The Battery You Need

The Impreza’s Keyless Access fob runs on a single CR2032 3-volt lithium coin cell — the standard 20 mm coin battery you can pick up almost anywhere. A quick look at the marking on the cell you remove confirms it, but on this generation it’s a CR2032. Spend a little on a decent branded cell; the cheapest ones sag under the momentary high current the transmitter needs and can give weak range even when brand new.

How to Change the Battery

1. Remove the metal key. Push the release catch on the back of the fob and slide the auxiliary blade straight out.
2. Part the halves. Work a small flat-blade screwdriver — tape the tip to save the plastic — into the gap the blade left, or into the seam running round the case, and twist gently until the fob separates.
3. Expose the cell. Lift the cover away to reveal the circuit board with the coin cell held under a small retaining clip.
4. Note, then replace. Check which face of the old CR2032 points outward before you slide it out from under the clip, then fit the new one the same way round, touching only its edge.
5. Reassemble. Squeeze the halves together until they click evenly all round, then slide the emergency key back until it clicks home.

⚠️ Copy the polarity of the old cell. Published guides for Subaru smart keys disagree on whether the positive side sits up or down, so don’t work from memory — match the orientation of the battery you just took out. Reversed, the cell can’t power the transmitter and may quietly drain against the contacts.

Confirm It Worked

Step back several metres and lock, then unlock, the car. Full range should snap back straight away, and the push-button start should read the fob as normal. The “Access key battery low” warning clears once the car next senses a healthy fob — occasionally at once, sometimes after a drive.

If a Fresh Cell Doesn’t Fix It

• Recheck battery and orientation. Make sure it’s a CR2032, sitting firmly under the clip and facing the same way as the old one.
• Clean the terminals. Corrosion or a smear of finger oil on the contacts often causes dropouts — a wipe with a dry cloth clears it.
• Use the emergency start. Press the start button with the fob held against it; if the car starts, the transponder is healthy and the fault lies with the battery or fob electronics rather than the car.
• Check the 12 V battery. A weak car battery can leave the Keyless Access system slow and looking like a fob fault, so have it tested if the Impreza is generally sluggish to wake.

New Key or Spare — Why It’s a Dealer Job

Changing the coin cell doesn’t disturb the fob’s pairing, so no reprogramming is needed and the remote works immediately. A replacement or spare Keyless Access fob is different: Subaru’s immobiliser must be reached with diagnostic equipment to register the new key, blanks are ordered against the VIN, and the emergency blade has to be cut to the car’s locks. That leaves adding a spare or replacing a lost key to a Subaru dealer or an established auto-locksmith. Keep the battery in your second fob fresh too, and you’re never reliant on a single working key.

Frequently Asked Questions

What battery does a Subaru Impreza (2017 onwards) key fob take?

The Keyless Access smart fob uses one CR2032 3-volt lithium coin cell. Confirm against the code printed on the old cell before buying a replacement.

Which way round does the battery fit?

Sources differ for Subaru smart keys, so the safe method is to note how the existing cell sits and install the new one in exactly the same orientation.

Will I need to reprogram the fob after a battery change?

No. Renewing the cell leaves the coding untouched, so the fob works right away. Only a brand-new key requires programming.

How long does the fob battery last?

Typically two to four years. Keeping the fob near the car so it constantly wakes the Keyless Access system shortens that.

The fob still won’t respond after a new battery — what next?

Re-check orientation and seating, then the contacts. If a known-good CR2032 still does nothing, the fob’s transmitter may have failed — rare next to a simple flat or upside-down cell.

Can I drive the Impreza with a dead fob battery?

Yes. Unlock with the emergency blade, then hold the fob against the start button as you press it — the transponder still works, so a flat cell won’t leave you stuck.

If the remote failed the moment the 12 V battery was disconnected — rather than fading gradually — the pairing is a likelier cause than the coin cell; check any stored fault code first on autodtcs.com.