These instructions apply to the BMW X3 Mk3 (G01) 2017-Present.
For other models, please choose your vehicle here.
If the remote on your BMW X3 (G01, 2017–present) only locks the car from arm’s length, needs a second press, or has stopped responding altogether, the coin cell inside it is the first thing to change — not the receiver, and not the immobiliser. Almost every G01 left the factory with BMW’s Comfort Access smart key: the smooth, button-topped fob with a metal emergency blade that slides out of one end. Some were ordered with the optional Display Key, the touchscreen fob that charges wirelessly — that one is covered further down. This guide walks through the standard smart key: how to spot a flat cell, the exact battery it takes, and how to open the case without cracking it.
How to Tell the Fob Battery Is Dying
- Shrinking range. You have to be right next to the X3 — or hold the fob against the door handle — before it reacts. This is the earliest and most reliable sign.
- A dashboard warning. The G01 puts a “Remote control battery low”-style message in the instrument cluster or Control Display when the key voltage drops, often with a key symbol. It usually appears a few weeks before the cell dies completely.
- Comfort Access gets flaky. Keyless unlocking by touching the handle, and push-button start, start working only intermittently — the car can no longer “see” the weak key reliably.
- Cold-morning dropouts. A cell that is nearly flat sags further in the cold, so the fob may fail on frosty mornings yet seem fine by midday.
A CR2032 in a BMW smart key typically lasts two to four years. If yours is around that age and doing any of the above, fit a fresh cell before assuming anything is wrong with the car.
The Battery You Need
The G01 Comfort Access smart key takes a single CR2032 — a 3-volt lithium coin cell, 20 mm across, the most common fob battery there is and stocked by every supermarket and hardware shop. Buy a fresh, good-quality branded cell; a cheap or old-stock CR2032 can sag under the brief high current the transmitter draws and give poor range even straight out of the packet. You do not need the older CR2450 that some BMW fobs use — that is the earlier diamond-shaped key, not the G01’s slide-blade smart key.
How to Replace the Battery in the Comfort Access Smart Key
- Slide out the emergency blade. Press and hold the small release catch on the side of the fob and pull the metal key blade straight out. It comes away completely — set it aside, as you’ll use it to open the case.
- Find the gap the blade leaves. Removing the blade exposes a slot at that end of the fob. This is the intended point to lever the two halves apart — there are no screws on this key.
- Split the case. Insert the tip of the emergency blade (or a small flat-blade screwdriver with tape wrapped round the tip to avoid scratches) into the slot and twist gently. Work along the seam and the two shells will separate with a soft click. Don’t force it in one spot — the plastic clips run around the edge.
- Note the orientation, then remove the old cell. Look at which way the coin cell faces before you touch it, and lift it out of its holder. Copy that exact orientation with the new one — the “+” face sits against the same contact.
- Fit the fresh CR2032. Handle it by the edges (skin oils shorten cell life), press it fully home under its clip so it can’t rock, and check it sits flat.
- Close and refit the blade. Press the two halves back together all the way round until they click, then slide the metal blade back in until it latches. Stand back and test lock, unlock and keyless start.
⚠️ Match the polarity of the cell you removed. A CR2032 fitted upside down won’t power the transmitter and, left in place, can slowly discharge against the contacts. If you didn’t note the direction, the marked “+” side of a coin cell almost always faces the removable clip or cover rather than the circuit board — but the safe rule is simply to copy the cell you took out.
A Note on the Optional Display Key
If your G01 came with the Display Key — the larger fob with a small LCD touchscreen — there is no coin cell to change. It has a sealed rechargeable battery that tops up wirelessly whenever the key sits in the charging pocket (under the centre console, on the driver’s side) or is placed on a Qi charger. If a Display Key stops holding charge after years of use, that’s a battery-ageing issue for a BMW dealer, not a home fix — but most owners simply keep it on charge and never think about it. Everything else on this page applies to the standard smart key.
Did It Work?
Walk a few metres from the X3 and lock, then unlock, using the buttons. Full range should be back instantly. For Comfort Access, confirm the car unlocks on a door-handle touch and starts on the button. The cluster’s “remote battery low” warning normally clears the next time the car reads a healthy key — sometimes after one drive cycle rather than the very first press.
If a Fresh Cell Doesn’t Fix It
- Re-check orientation and seating. An upside-down or loosely-clipped cell is the number-one reason a “new” battery does nothing. Reopen and confirm it matches the way the old one sat and is pressed fully home.
- Clean the contacts. A film of finger grease or light corrosion on the terminals is enough to cause dropouts. Wipe both the cell faces and the metal contacts with a dry cloth.
- Warning still showing? Drive the car a short distance so the system re-reads the key a few times. If Comfort Access alone is unreliable while the buttons work, that can point to the car’s antenna or a low 12 V vehicle battery rather than the fob.
New Key or Spare — Why It’s a Dealer Job
Changing the battery keeps the key’s existing coding, so the fob keeps working with no reprogramming. Adding a spare or replacing a lost key is different: a BMW smart key is tied to the car’s immobiliser and has to be ordered against the VIN and coded to the vehicle with BMW diagnostic equipment. That makes it a job for a BMW dealer or a properly equipped auto-locksmith. Keep the battery in your spare key fresh too, so you’re never left relying on a single working fob.
Frequently Asked Questions
What battery does a BMW X3 G01 key fob take?
The standard Comfort Access smart key uses one CR2032 3-volt lithium coin cell. The optional Display Key has no user-replaceable battery — it charges wirelessly instead.
Is it a CR2032 or a CR2450?
For the G01’s slide-blade smart key it’s a CR2032. The CR2450 belongs to BMW’s older diamond-shaped fobs, not this generation — if in doubt, read the code printed on the cell you remove and match it.
Do I need to reprogram the key after a battery change?
No. The battery only powers the remote; the coding stays intact, so the fob works the moment you close it back up. Reprogramming is only needed for a brand-new key.
How do I open the fob without breaking it?
Slide the metal emergency blade out first, then use that blade (or a taped flat screwdriver) in the slot it leaves to gently prise the two halves apart. There are no screws — it’s all plastic clips around the seam.
How long should the key battery last?
Usually two to four years. Frequent remote use, or leaving a Comfort Access key sitting close to the car so it wakes constantly, shortens that.
Can I still drive the X3 if the fob battery is completely dead?
Yes. Unlock the driver’s door with the emergency blade hidden in the fob, then hold the key against the marked spot on the steering column (or in the tray, per your handbook) and press start — the car reads the transponder even with a flat cell, so a dead battery won’t strand you.
If the remote quit suddenly right after the car’s 12 V battery was disconnected or went flat — rather than fading over weeks — the fault is more likely the vehicle side than the coin cell, and the car may have logged a fault code worth checking. You can look up what any stored code means on autodtcs.com.
Independent guide — not affiliated with BMW. Always follow your official service manual and safety precautions. Read our full disclaimer.