Mazda Key Fob Battery Replacement: Which Battery (CR2025, CR1620) and How to Change It
Mazda is the odd one out: its push-button smart keys take a CR2025, not the CR2032 most other brands use, and the older flip keys take a thin CR1620. A CR2032 will go into a Mazda smart key but it is 0.7 mm too thick, so the case does not close properly and the contacts get strained. Read the code on the old battery before you buy. To open the smart key, slide the catch and pull out the emergency key, then twist a flat tool in the slot it came from. Fit the new battery the same way round, close the case and press lock to test. No reprogramming is needed.
The most common mistake with a Mazda key is buying the wrong battery, because the CR2032 everyone keeps in a drawer does not belong in it. Once you have the right cell the swap takes five minutes. This guide tells you which battery each Mazda key takes, how to open each style without marking the case, how to start the car when the fob is dead, and what to check if a new battery does not bring it back.
Which battery your Mazda key fob takes
| Key style | Typical FCC ID | Common on | Battery |
|---|---|---|---|
| Flip key or separate remote (older cars) | KPU41788, KPU41846, BGBX1T478SKE125-01, SKE12501 | Mazda3 2004 to 2013 (keyed), Mazda6 2003 to 2013 (keyed), Mazda5, CX-7, CX-9 2007 to 2015 (keyed), Tribute, MX-5 2006 to 2015, Mazda2 | CR1620 |
| First smart key (rounded, 2007 to 2013) | BGBX1T458SKE11A01, KR55WK49383, SKE11A01 | Mazda3 2010 to 2013, Mazda6 2009 to 2013, CX-7 2010 to 2012, CX-9 2010 to 2015, RX-8, MX-5 2009 to 2015 with advanced keyless | CR2025 |
| Current smart key (flat, 2013 on) | WAZSKE13D01, WAZSKE13D02, WAZSKE13D03, WAZSKE11D01, WAZSKE13D04 | Mazda3 2014 on, Mazda6 2014 on, CX-5 2013 on, CX-3, CX-30, CX-50, CX-9 2016 on, CX-70, CX-90, MX-5 2016 on, MX-30 | CR2025 |
Mazda’s owner’s manuals list CR2025 for the key. If you only have a CR2032 to hand it may work for a while, but the back cover will not sit flush and the contact spring is bent further than it should be. Buy the CR2025. The code on the flat + face of the old battery is the final word.
The first two digits of a coin cell code are the diameter in millimetres and the last two are the thickness in tenths of a millimetre, so CR2025 and CR2032 share a diameter and differ only in thickness. Our CR2032 vs CR2025 guide explains why that matters and the key fob battery size chart covers every common size.
What you need
- One new CR2025 (or CR1620 for a flip key). Panasonic, Energizer, Duracell or Murata; Mazda dealers sell the same cells
- A small flat-blade screwdriver or a plastic pry tool
- A clean surface with good light so the rubber button pad does not go missing
Skip rechargeable LIR cells. They have the same shape but a higher voltage than the fob is built for.
Changing the battery in a Mazda smart key
This covers the current flat key (2013 on) and the earlier rounded one. Both take a CR2025.
Slide the release catch on the back of the fob and pull the metal key straight out. You will use its tip in the next step.
Look into the slot the emergency key came out of. There is a notch for a flat tool. Put the key tip or a small flat screwdriver into it and twist. The back cover lifts away. Mazda suggests wrapping the tool tip in tape to protect the plastic; staying in the slot rather than prying round the outside is the main thing.
On the flat key, a thin inner cover sits over the battery. Lift it off with a fingernail. Note which way the battery faces; on Mazda keys the + side with the code faces up towards you.
Lever it up at the cut-out beside it with the key tip or a plastic tool and lift it out by the edge. Keep metal tools off the circuit board.
Hold it by the edge and press it in the same way round. It should sit flat without rocking. Refit the inner cover.
Snap the back cover on so the seam is flush all round, slide the emergency key back in until it clicks, and press lock and unlock. The LED flashes with each press when the battery is good.
Changing the battery in a Mazda flip key
- Press the button to fold the blade out. Look along the seam of the plastic head for a small slot, usually at the end opposite the blade or beside the pivot.
- Put a flat screwdriver or coin in the slot and twist gently. The back cover comes away.
- Note which way the CR1620 faces, then lever it out at the cut-out beside it.
- Press in the new CR1620 the same way round, check the rubber button pad is seated flat, and snap the cover back on.
The immobilizer chip that lets the car start is sealed in the key head and does not use the battery. A flip key with a dead battery still turns the ignition and starts the engine.
CR2025 3V lithium coin battery (Mazda smart keys)
Mazda smart keys take the thinner CR2025, not a CR2032. Older flip keys take a CR1620. Buy a name brand in a small multi-pack and check the date on the pack.
Flip keys: CR1620
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Do you need to reprogram a Mazda key after a battery change?
No. The pairing is stored in memory that does not need battery power, so the fob works as soon as the new cell is in. If the dash showed the key warning light or a Key battery low message, it clears after the next start or two. Programming is only needed for a key that is new to the car.
If the car still says the key is not detected
First, start the car. On a push-button Mazda, hold the fob so the buttons face you and touch the back of it to the Start button; the key warning light changes and the car chimes to say it has read the chip. Press the brake and push Start within a few seconds. On older Mazdas with a key slot on the dash, insert the fob in the slot instead. The emergency key blade opens the driver’s door.
Then check, in this order:
- Battery size. A CR2032 in a Mazda key stops the cover seating and can bend the contact; a CR2016 sits loose. Compare the new code with the old one.
- Battery upside down. No LED flash at all usually means the cell is reversed.
- Flattened contact. The spring contact can be pressed down while prying, and is often already bent if a CR2032 was forced in earlier. Lift it gently with a plastic tool and wipe it with a dry cotton bud. See how to clean key fob battery contacts.
- A flat new battery. Unbranded multi-pack cells and cells that have sat for years can be dead in the packet. Try one from a fresh, dated pack.
- The car’s 12 V battery. If the car was also slow to crank, the key is not the problem. See can a bad car battery cause key fob problems.
- Damage inside the fob. A fob that has been dropped hard, through the wash or left on a hot dash can have a cracked solder joint. A locksmith can test whether it still transmits before you pay for a new key.
The full checklist is in Mazda key fob not working and key fob not working after a battery replacement.
What it costs
Most Mazda parts counters will fit a battery while you wait for the price of the cell plus a few dollars, and some do it free during a service visit. The larger figures only apply when the key itself has to be replaced, which a battery change almost never leads to.
How long the new battery will last
A flip key only transmits when you press a button, so its CR1620 normally lasts two to three years. A smart key listens for the car and answers every time you touch a handle, and the CR2025 holds less energy than a CR2032, so expect roughly one to two years. Cold winters, leaving the fob within a few feet of the car overnight, and carrying it loose where items press the buttons all shorten that. See how long key fob batteries last for a sensible replacement schedule.
Safety: keep coin batteries away from children and pets
A swallowed coin cell can cause serious internal burns within hours. Keep spares and the old cell out of reach, and take old batteries to a drop-off point rather than household waste. If you think a child has swallowed a battery, go to the emergency room straight away and call the National Battery Ingestion Hotline at 1-800-498-8666, or Poison Help at 1-800-222-1222.
Frequently Asked Questions
Mazda smart keys, both the current flat key and the earlier rounded one, take a CR2025. Older flip keys and separate remotes take a CR1620. Confirm with the code on the old battery.
It is not recommended. A CR2032 is 0.7 mm thicker than the CR2025 the key is designed for, so the cover does not sit flush and the contact spring is over-bent. It may work briefly but buy the CR2025.
Slide the catch and remove the emergency key, then twist the key tip or a small flat screwdriver in the notch inside the slot it came from. The back cover lifts off, and a thin inner cover over the battery lifts out with a fingernail.
No. Mazda keys keep their pairing without battery power. The fob works as soon as the new battery is in, and the key warning clears after the next start or two.
Touch the back of the fob to the Start button until the car chimes, then press the brake and push Start within a few seconds. Older Mazdas have a key slot on the dash to put the fob in instead. Use the emergency key blade to open the driver’s door.
Check that the new cell is a CR2025, the right way up, and from a fresh pack, and that the contact spring was not flattened. If the fob LED flashes but the car ignores it, use the backup start and have a locksmith test the fob.