Replace the Key Fob Battery

If the remote on your Ford Focus (Mk2, 2004–2012) only works from close up, needs several presses, or has stopped locking the car, a flat coin cell in the fob is almost always the cause — and it is a quick driveway change. The Mk2 came with two fob styles, and both take the same battery.

First, Rule Out the Battery

A weak fob battery is the number-one reason a Focus remote becomes unreliable: short range, needing a second or third press, or the lock/unlock buttons dropping out altogether. The Focus Mk2 fob uses a CR2032 3V lithium coin cell — a common, inexpensive battery. Fit a fresh one before suspecting anything more serious.

Replacing the Fob Battery

Check which of the two fob styles you have, then follow the matching steps. Both use a CR2032 fitted the same way up.

1. Type 1 (remote unit clips onto the key): insert a small flat screwdriver at the seam and unclip the remote-control unit from the main key, then separate the two halves of the case. Lift out the old cell and fit the new CR2032 with the positive (+) side facing upwards. Reassemble in the reverse order.
2. Type 2 (integrated key): press and hold the buttons, remove the key cover and slide out the metal key, then insert a small screwdriver to split the case. Take out the old transmitter cell and fit the new CR2032 positive (+) side up. Refit the key and cover.

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

Lost Key or Adding a Spare

There are two separate things inside a Focus key, and they behave differently. The remote (button) function can be re-taught to the car with an ignition-key sequence, so a remote that has lost sync can often be paired again at home. But the immobiliser transponder chip in a brand-new or replacement key must be coded with Ford diagnostic equipment — there is no owner sequence for that part. So renewing the battery in a key that already works is a home job, while a genuinely new, spare or lost key has to be cut and coded by a Ford dealer or an auto-locksmith.

If a Fresh Battery Doesn’t Fix It

• Check the polarity — the CR2032 must go in positive (+) side up. A cell fitted upside down gives no response at all.
• Use the metal key blade to unlock the door, and remember the Mk2 is a twist-key car — a flat fob never stops it starting, so put the blade in the ignition and start as normal.
• Still nothing from any key? A receiver or body-control fault may be involved rather than the fob — check the stored code on autodtcs.com.

Frequently Asked Questions

What battery does the Focus Mk2 key take?

A CR2032 3V lithium coin cell, fitted positive (+) side upwards. Both fob styles used on the Mk2 take the same cell.

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

No. The remote keeps its programming through a battery change — just fit the CR2032 the right way up and test the buttons.

Can I program a new Focus Mk2 key myself?

Only partly. The remote-button function can be re-synced with an ignition-key sequence, but the immobiliser chip in a new key needs Ford diagnostic equipment, so a new, spare or lost key must be coded by a dealer or auto-locksmith. Renewing the battery in a working key is the part you can do at home.

How do I start the car if the fob is completely dead?

Unlock the driver’s door with the hidden metal blade, then put the same blade in the ignition and turn it. The Focus Mk2 has no push-button start, so a flat fob battery never prevents starting.

If the remote stopped working after a battery disconnection, see our Ford Focus battery disconnect/reconnect guide.