Replace the Key Fob Battery

Last updated: June 5, 2026

If the remote on your Honda Civic Mk9 (FK, 2012–2017) only works from up close, or has stopped locking the car altogether, the fob’s coin battery is almost always the cause — and replacing it is a two-minute job. This guide covers swapping the key fob battery and explains what you can and cannot do yourself when it comes to a lost or extra key.

First, Rule Out the Battery

A weak fob battery is the number one reason a Civic remote becomes unreliable — short range, needing several presses, or no response. Before assuming anything more serious, fit a fresh cell. Check the old cell when you open the fob to confirm the type (most use a CR-series coin cell).

Replacing the Fob Battery

1. If your fob has a fold-out mechanical key, slide it out — this often releases the case.
2. Remove the small screw(s) holding the fob together (the Civic fob is screwed, not just clipped), then separate the upper section of the case.
3. Lift the transmitter out of its holder and remove the old coin cell, taking care not to touch the terminals.
4. Fit the new cell observing the correct polarity (the same way the old one sat).
5. Refit the transmitter, clip the cover back on and refit the screw(s).
6. Test that the remote locks and unlocks the car. The range should be back to normal.

After a battery change the remote keeps its programming — you do not need to re-pair it.

Lost Key or Adding a Spare — What You Can’t Do at Home

The Civic Mk9 cannot have a key programmed without a diagnostic tool. Up to six keys can be registered to the car, but pairing a new or replacement key must be done by a Honda dealer or an auto-locksmith with the right equipment — there is no key-and-ignition sequence that does it. So the home job is limited to renewing the battery in a fob that already works.

If a Fresh Battery Doesn’t Fix It

• Check the cell polarity and contacts — a cell fitted the wrong way or dirty contacts will give no response.
• Use the mechanical key hidden in the fob to get into the car if the remote is dead.
• Still nothing from either fob? The receiver or a body-control fault may be involved — the car can store a code you can look up on autodtcs.com before booking a diagnosis.

Tools and Parts

• A small screwdriver to remove the fob screw(s) and split the case.
• A fresh coin cell of the correct type (check the old one when you open the fob).

Frequently Asked Questions

What battery does the Civic Mk9 key fob take?

A CR-series coin cell — check the old one when you open the fob to confirm the exact size before buying.

Do I need to reprogram the remote after changing the battery?

No — the programming is retained. Just fit the new cell the correct way round and test it.

Can I program a new Civic key myself?

No — the Mk9 Civic requires a diagnostic tool to register a key, so a new or replacement key must be coded by a Honda dealer or a locksmith.

The fob is screwed together — is that normal?

Yes — the Civic fob uses a small screw as well as clips, so remove it before trying to separate the case to avoid breaking the tabs.

If the remote stopped working after a battery disconnection, see our Honda Civic Mk9 battery disconnect/reconnect guide.