These instructions apply to the Honda Jazz Mk4 (GR) 2020-Present.
For other models, please choose your vehicle here.
When the smart key on your Honda Jazz Mk4 (GR, 2020–present) — badged Fit in some markets and sold here only as a hybrid (e:HEV) — starts working from just a step away, or the dash flashes up a key-battery warning, the culprit is almost always the coin cell in the fob rather than the car. Every Mk4 Jazz comes with the same keyless smart key (proximity locking and push-button start, with a slide-out emergency blade), so there’s only one procedure to learn. It opens a little differently from most fobs — the case is genuinely stiff and wants a coin twisted in a specific gap — and getting that right saves you from prying at the wrong seam. Here is the exact cell, how to crack the case cleanly, and why a spare key still means a dealer visit.
How to Tell the Fob Battery Is Dying
- Range shrinks first. You end up standing right at the door, or holding the fob to the handle, before it locks or unlocks — the classic first sign.
- Walk-up entry stops working. The Jazz normally unlocks when you touch the handle with the key on you; when the cell weakens you have to press the button instead, then eventually that gets patchy too.
- A dash warning. The Mk4 shows a low key-battery message (a key symbol with the wording about a low remote/key battery) in the driver’s display when the fob is weak.
- Cold-weather flakiness. A tired cell that copes in mild weather can drop out on a cold morning; intermittent response when it’s freezing is a near-flat battery.
A coin cell in a Jazz smart key usually lasts two to three years — keyless fobs run their battery down a bit faster than plain remotes because they wake whenever they’re near the car. If yours is around that age and misbehaving, change the cell before you suspect anything deeper.
The Battery You Need
The Honda Jazz Mk4 smart key takes a CR2032 3-volt lithium coin cell — the common, widely stocked size you’ll find in any supermarket, hardware shop or newsagent. Buy a quality branded cell (Panasonic, Sony/Murata, Energizer or Duracell); the brief burst of current the transmitter needs makes cheap cells sag, which shows up as short range even when the battery is fresh out of the packet.
How to Change the Jazz Smart Key Battery
- Slide out the emergency blade. Push the small release catch on the fob and pull the metal auxiliary key straight out. You don’t strictly open the case through the blade slot on this fob, but removing the blade gets it out of the way and is where the release lives.
- Find the gap between the two plastic blocks. On the back edge, near where the blade sat, there’s a narrow slot between two moulded blocks of plastic. That’s the intended opening point — not the main body seam.
- Twist a coin in that gap. Insert a coin (or a flat screwdriver — several owners find the screwdriver easier) into the slot and twist to lever the halves apart. Wrap the coin in a cloth if you want to protect the case. This fob is genuinely stiff, so expect to use firm, steady force — that’s normal, not a sign you’re doing it wrong.
- Separate the shells. Once it releases, lift the back off to expose the CR2032 in its holder on the circuit board.
- Note the orientation, then remove the old cell. Check which face is visible before you lift it out, then ease the old battery from under its clip. Follow the +/− markings in the holder and match what you removed.
- Fit the fresh CR2032 and close up. Seat the new cell the same way round, press the two halves back together until they click all the way round, and slide the emergency blade home until it latches.
⚠️ Watch the polarity. A coin cell fitted upside down won’t power the fob, and if it’s left in it can slowly drain against the contacts. When in doubt, the correct face is the one that lines up with the + symbol moulded into the battery holder — don’t fit it by guesswork.
Confirm It Worked
Step back a few metres and lock, then unlock, the Jazz with the buttons — full range should be back instantly. Then test the keyless side: with the fob in your pocket, touch the door handle to lock and unlock, and press the start button to confirm the car reads it. The low-key-battery message clears the next time the car reads a healthy fob, which may be after a short drive rather than the moment you close the case.
If a Fresh Cell Doesn’t Fix It
- Re-check seating and polarity. The commonest DIY slip-ups are an upside-down cell or one not pushed fully under its clip — open it back up and confirm.
- Clean the contacts. A dry cloth or cotton bud on the terminals clears finger grease or light tarnish that can cause dropouts.
- Use the backup start. If the car won’t detect the fob, hold it against the start button and press — the Jazz can read the transponder at close range even with a flat cell, which confirms the battery was the issue.
- Still no life from the remote? A weak car 12 V battery can imitate key faults; if the whole car is slow to wake, have the vehicle battery tested before blaming the fob.
New Key or Spare — Why It’s a Dealer Job
Swapping the coin cell keeps the fob’s coding intact, so there’s no reprogramming to do — the smart key works as soon as the case clicks shut. A genuinely new key is another story: Honda’s smart-key system pairs each fob to the car’s immobiliser electronically, blank fobs are ordered against the VIN, and the emergency blade must be cut to the car’s key code. That pairing needs Honda diagnostic equipment, so a spare or a lost-key replacement is a job for a Honda dealer or an auto-locksmith. Keep your spare fob’s battery fresh as well and you’ll never be stuck with a single working key.
Frequently Asked Questions
What battery does a Honda Jazz Mk4 key fob take?
A single CR2032 3-volt lithium coin cell — the widely available standard size, so you can pick one up almost anywhere.
How do I open the Jazz smart key — it feels stuck?
Twist a coin (or a flat screwdriver) in the narrow gap between the two plastic blocks near the emergency-blade slot, not the main body seam. This fob is stiff by design, so firm, steady force is normal.
Which way up does the battery go?
Match the cell you removed and follow the +/− symbols moulded into the holder. Note the orientation before you lift the old one out so you can’t get it wrong.
Do I need to reprogram the key after changing the battery?
No. The coding isn’t affected by a battery swap, so the smart key works immediately. Only a brand-new key needs pairing to the car.
How long should a Jazz key battery last?
Typically two to three years. Because the keyless system wakes the fob whenever it’s near the car, storing the key right by the car overnight shortens the cell’s life.
Can I still drive if the fob is completely dead?
Yes. Use the emergency blade in the fob to unlock the driver’s door, then hold the fob against the start button and press — the car reads the transponder up close, so a flat cell won’t leave you stranded.
If the Jazz’s remote failed suddenly rather than fading — particularly just after the 12 V battery was disconnected — suspect a pairing or electrical fault over the cell, and any stored trouble code will help you narrow it down. You can check what a dashboard fault code means on autodtcs.com.
Independent guide — not affiliated with Honda. Always follow your official service manual and safety precautions. Read our full disclaimer.