These instructions apply to the Fiat 500X Mk1 (334) 2015-present.
For other models, please choose your vehicle here.
When the remote on a Fiat 500X (Type 334, 2015–present) only locks the car from arm’s length, needs a second press to respond, or has stopped working altogether, the coin cell inside the key is almost always the reason. The 500X shipped with one of two keys depending on trim and year — the common folding “flip” remote (shared with the Jeep Renegade it’s built alongside) or, on higher trims and remote-start cars, a keyless smart fob you never take out of your pocket. Both run on the same battery but open in completely different ways. Here is the exact cell you need, how to open each key, and why cutting a brand-new one is the single job you can’t finish at home.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to be right beside the 500X — or hold the key against the door handle — for it to lock or unlock. This is the first and clearest warning.
- A dash “key battery low” message. The 500X normally shows a low-key-battery alert in the instrument cluster while the fob still has a little charge left, giving you a few weeks’ notice before it goes flat.
- Intermittent button response. A press that works one time in three, especially on cold mornings, is a near-flat cell that can no longer supply the brief burst of current the transmitter needs.
- Keyless entry stops recognising the fob. On smart-key cars the door handle no longer unlocks on touch and the start button reports “key not detected” — a weak proximity cell is the usual cause.
A CR2032 in a 500X key typically lasts two to four years. If yours is older than that and doing any of the above, fit a fresh cell before you start suspecting the car’s receiver or immobiliser.
The Battery You Need
Both the folding flip remote and the keyless smart fob take a single CR2032 3-volt lithium coin cell — the most common key battery there is, sold in any supermarket, hardware shop or petrol station. Buy a fresh, good-quality branded cell: cheap or old-stock CR2032s sag under the short high-current pulse the transmitter draws and can give poor range even straight out of the packet. One battery type covers every 500X key, so you don’t need to know which fob you have before you buy.
Method 1 — Folding “Flip” Remote
- Press the release and flip the metal key blade fully open so it’s out of your way and the fob is easier to hold.
- Find the small battery-holder catch on the fob body. Slip the tip of a fine flat-blade screwdriver into it and twist gently to unlock the holder — the printed arrow points out toward the metal blade.
- Ease the battery holder out of the fob, then lift the old CR2032 from the holder.
- Drop the new cell into the holder with the positive (+) side facing up, exactly as the old one sat — don’t flip it over.
- Slide the back of the holder into the fob first, press the rest home until it seats, then twist the lock closed. Test every button.
Method 2 — Keyless Smart Fob
- Release the emergency blade: slide the small catch on the back of the fob and pull the mechanical key straight out with your other hand.
- Insert a flat-blade screwdriver or a coin into the seam the blade leaves behind and gently prise the two halves of the case apart. Work slowly so you don’t tear the rubber seal that keeps the fob water-resistant.
- Lift out the old CR2032. The new cell goes in with the positive (+) side up — match the (+) mark on the battery to the (+) mark moulded into the clip on the back cover.
- Try not to touch the flat faces of the new cell with bare fingers; skin oils shorten its life.
- Line the halves up and press them together until they click all the way round, then slide the emergency blade back in until it latches.
⚠️ Get the polarity right. On both 500X keys the CR2032 sits positive-side up. A cell fitted upside down won’t power the transmitter and can slowly discharge against the contacts — so always copy the orientation of the cell you took out.
Make Sure It Took
Stand back several metres and lock, then unlock, the car. Full range should return the instant the fresh cell is in. On a keyless 500X the door handles should respond to a touch again and the start button should read the fob straight away; the “key battery low” message clears once the car has read a healthy fob, occasionally after one short drive rather than immediately.
If a Fresh Cell Doesn’t Fix It
- Re-check the orientation and seating. The cell must sit positive-side up and press firmly under its clip or holder against clean metal — a battery that’s a hair proud of its contact gives exactly the same dropouts as a flat one.
- Wipe the contacts. A smear of finger grease or light corrosion on the terminals is enough to cause weak or intermittent response; clean them with a dry cloth.
- Confirm the cell is genuinely good. Old-stock or bargain CR2032s can read close to 3 V yet collapse under load — try a second branded cell before assuming the worst.
- Still nothing? If a known-good battery brings no life at all, the fob’s transmitter or a lost pairing may be at fault. A weak car 12 V battery can also mimic key trouble — if the 500X itself is slow to wake, rule that out first.
New Key or Spare — Why It’s a Dealer Job
Changing the coin cell doesn’t touch the fob’s coding, so the remote keeps working the moment the new battery is in — no reprogramming needed. Cutting or coding a new key is a different matter. The 500X’s immobiliser has to be accessed with FCA-compatible diagnostic equipment, and blank flip or smart fobs must be matched to the car’s VIN before they’ll start it. That makes adding a spare or replacing a lost key a job for a Fiat dealer or an auto-locksmith — so keep the battery in your spare fresh too, and you’re never down to a single working key.
Frequently Asked Questions
What battery does a Fiat 500X key fob take?
A single CR2032 3-volt lithium coin cell. It’s the same size whether you have the folding flip remote or the keyless smart fob, so one battery covers every 500X key.
Which way up does the battery go?
Positive (+) side up in both key types. Match the (+) mark on the cell to the (+) mark inside the holder or clip, and copy how the old one was sitting before you remove it.
Do I have to reprogram the key after changing the battery?
No. A battery swap leaves the fob’s coding untouched, so it works straight away. Only a brand-new key needs programming to the car.
How do I open the Fiat 500X flip key?
Flip the metal blade open, then use a fine flat screwdriver to twist the battery holder’s catch and draw the holder out. The smart fob is different: slide out the emergency blade first, then prise the two case halves apart.
How long should a 500X key battery last?
Usually two to four years. Heavy remote use, or leaving a keyless fob sitting close to the car so it wakes constantly, will shorten that.
Can I still drive the 500X if the fob battery is completely dead?
Yes. Use the emergency blade inside the fob to unlock the driver’s door. On keyless cars, hold the fob against the start button (the car reads the transponder directly) and it will start even with a flat coin cell, so a dead battery won’t strand you.
If the remote died suddenly right after the car’s 12 V battery was disconnected — rather than fading over weeks — the pairing or a stored fault is a likelier cause than the coin cell. You can look up what any logged code means on autodtcs.com.
Independent guide — not affiliated with Fiat. Always follow your official service manual and safety precautions. Read our full disclaimer.