Replace the Key Fob Battery

If the remote for your Volvo V40 (2012–2019) only locks the car from arm’s length, has stopped flashing its LED, or has gone quiet, the coin cell inside it has almost certainly run flat. The second-generation V40 shipped with two different keys: a plain remote control key and the PCC (Personal Car Communicator) — the fatter fob with the “i” information button and small indicator lamps at the corners. They open the same way and take the same size of cell, but here is the catch that trips people up: the ordinary remote holds one battery while the PCC holds two, seated in opposite directions with a plastic spacer between them. Get that wrong and the key stays dead even with fresh cells in it. Below is the exact procedure, how to tell a flat cell from a real fault, and why a brand-new key is the one job you can’t finish at home.

How to Tell the Fob Battery Is Dying

• Shrinking range. You end up standing right beside the car — or holding the fob against the door handle — before it will lock or unlock. This is the classic first warning.
• No LED on a button press. The V40 remote flashes its indicator when you press lock or unlock. Once the cell is too weak, that light stops — a quick way to confirm the fob, not the car, is the problem.
• A key-battery warning in the display. On keyless V40s the driver’s information display shows a low remote-key-battery message when a cell is running down; the car will tell you to change it.
• Cold-weather dropouts. A cell that is nearly done struggles in winter, so buttons that work in a warm garage fail on a frosty morning.

A CR2430 in a V40 remote usually lasts two to four years. If yours is around that age and doing any of the above, fit a fresh cell before suspecting the receiver or the immobiliser.

The Battery You Need

The Volvo V40 remote — both the plain remote key and the PCC — uses the CR2430 3-volt lithium coin cell. Note the code carefully: it is not the more common CR2032, and it is not the CR2450 that some older Volvo smart keys used, so a battery grabbed off a supermarket shelf without checking may not fit. The important difference is quantity:

• Plain remote control key — one CR2430.
• PCC (with the “i” button and corner lamps) — two CR2430 cells.

Buy good-quality branded cells. Cheap ones sag under the brief high current a transmitter draws and can give short range even when supposedly “new”. If you own a PCC, buy a two-pack so both cells are fresh — mixing an old and a new one shortens the life of both.

Method — Opening the V40 Remote (Remote Key and PCC)

1. Release the emergency key blade. Slide the spring-loaded catch on the fob to the side and, at the same time, pull the metal key blade straight out backwards. Keep this blade — you use it to lock the car and you need the empty slot to reassemble the fob.
2. Open the shell. Insert a small (about 3 mm) flat-blade screwdriver into the hole left behind the spring-loaded catch and gently prise the two halves of the key apart. Work slowly; the case is plastic and the halves separate with light leverage, not force.
3. Turn it buttons-up before you finish opening. Once the shell parts, turn the fob so the buttons face upward. This stops the loose cells (and, on the PCC, the little white plastic spacer) from dropping out and getting lost.
4. Note the layout, then remove the old cell(s). Carefully prise out the battery. On a PCC, note the order — two cells with a white plastic tab sandwiched between them — before you disturb anything.
5. Fit the new cell(s), the right way up. On the plain remote key, install one CR2430 with the (+) side facing down. On the PCC, install the first cell (+) side up, seat the white plastic spacer on top of it, then install the second cell (+) side down.
6. Close and relock the blade. Press the two halves of the key firmly back together until they click. Hold the fob with the blade slot pointing up, lower the metal blade into its slot and press lightly — you should hear it click home — then test every button.

⚠️ Orientation matters, especially on the PCC. The two cells face opposite ways with the plastic tab between them; put them both in the same way, or leave the spacer out, and the key will not power up. Copy the layout you removed, and if in doubt fit the first cell positive-up and the second positive-down as above.

Did It Work?

Stand back a few metres and lock, then unlock, the car. Full range should return straight away and the LED should flash cleanly on each press. If your V40 had shown a low-key-battery message, it clears once the car next reads a healthy fob — sometimes after a drive cycle rather than the instant you refit the cell.

If a Fresh Cell Doesn’t Fix It

• Re-check orientation and the spacer. On the PCC this is the single most common mistake — both cells must face opposite ways with the white tab between them, exactly as they came out.
• Wipe the contacts. A smear of finger grease or a trace of corrosion on the terminals is enough to cause dropouts; clean them with a dry cloth and make sure each cell sits firmly under its clip.
• Try the backup start. If a keyless V40 will not detect the fob at all, hold the remote against the marked spot on the steering column or start console — the car can read a fob with a weak signal at close range, which confirms the transmitter still lives.
• Rule out the car’s own battery. A tired 12 V battery can make a V40 slow to wake and mimic a key fault; if the car itself is sluggish to respond, have the main battery checked.

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

Changing the cell keeps the fob’s existing coding, so nothing needs reprogramming afterwards. Adding a spare or replacing a lost key is a different matter: a blank V40 remote has to be ordered against the car’s VIN, the metal blade cut to the car, and the fob married to the immobiliser with Volvo diagnostic equipment. That puts a new or spare key in the hands of a Volvo dealer or a properly equipped auto-locksmith — so keep the battery in your spare fresh too, and you are never down to a single working key.

Frequently Asked Questions

What battery does a Volvo V40 key fob take?

A CR2430 3-volt lithium coin cell. The plain remote key uses one; the PCC (the fob with the “i” button and corner lamps) uses two of them.

Does the V40 PCC really need two batteries?

Yes. The PCC holds two CR2430 cells with a white plastic spacer between them. Replace both at once, and make sure the first goes in positive-side up and the second positive-side down.

Which way up do the cells go?

On the plain remote, the single CR2430 sits positive (+) side down. On the PCC, the first cell is positive up, the spacer sits on top, and the second cell is positive down. Fit them the wrong way and the key will not work.

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

No. A battery swap leaves the coding untouched, so the fob works as soon as you refit the blade. Only a brand-new key needs programming to the car.

How long should a V40 key battery last?

Typically two to four years. Heavy use of the remote, or leaving a keyless fob sitting close to the car so it wakes constantly, brings that down.

Can I still drive the V40 if the fob is completely dead?

Yes. Pull the metal blade from the fob to unlock the driver’s door, then hold the remote against the marked reader spot inside to start — the keyless system is designed to read a flat fob at close range, so a dead cell will not strand you.

If your V40’s remote quit suddenly right after the car battery was disconnected — rather than fading over weeks — the cause is more likely the electronics than the coin cell, and the car may have logged a fault code worth reading before you replace anything. You can look up what a stored code means on autodtcs.com.