Start the Car With a Dead Key Fob Battery

When the remote on your BMW X3 (G01, 2017–Present) stops responding – no keyless unlock, a “key battery low” message, or Comfort Access that ignores the door handle – the small coin cell inside the fob has run down. The G01 has no dashboard key slot, so the procedure is to unlock with the hidden blade and then start the engine by holding the fob against a reader in the steering column. Here is how to do both without calling for help.

Unlock the door with the emergency key blade

A flat fob cannot work the central locking, so the metal blade hidden inside it is your route in.

1. Slide the release catch at the base of the fob and withdraw the metal emergency blade.
2. At the driver’s door, note there is no exposed keyhole. The lock barrel sits under a trim cap at the rear of the door handle.
3. Insert the blade into the small recess beneath the handle and lever the cap off to reveal the cylinder.
4. Turn the blade in the cylinder to unlock the driver’s door, then clip the cap back on so it is not lost.

Expect the alarm to chirp or sound when you open the door this way; it stops once the car recognises a valid key inside.

Start the engine by holding the fob to the steering column

The G01 reads the fob’s transponder through a ring antenna built into the steering-column trim.

1. Get in, close the door, and press the brake pedal.
2. Find the small key symbol embossed on the steering-column surround – on the X3 it is on the right-hand side of the plastic.
3. Press the flat back of the fob firmly against that symbol so it touches the plastic directly.
4. With the fob held in place and the brake down, press the Start/Stop button. The car powers the chip and the engine starts.
5. No response? Shift the fob a few millimetres or turn it over – the transponder coil has to line up with the antenna behind the symbol.

Why the chip starts the car, not the blade

Only the remote-control side of the fob – locking, tailgate, Comfort Access – depends on the coin cell. Engine authorisation comes from a passive transponder that needs no battery; the column antenna energises it and reads its rolling security code to release the immobiliser. The blade carries no code, so it can open a door but never crank the engine. That is by design and is the same on every keyless G01.

Replace the fob battery (CR2032)

With the car running again, fit a fresh cell to restore keyless operation.

1. Pull the emergency blade out; the gap it leaves is the opening point for the case.
2. Ease the two halves of the housing apart along the seam until the back cover comes free.
3. Lift out the spent CR2032 coin cell, noting its orientation, and press the new one in to match.
4. Close the case, refit the blade, and lock/unlock the X3 to confirm the remote is alive again.

If the warning persists with a new cell, clean the battery contacts with a dry cotton bud, as corrosion can mimic a weak battery.

Frequently Asked Questions

Does the X3 G01 have a key slot to insert the fob? No. The G01 uses only the steering-column reader, so there is nowhere to push the fob in – hold it against the key symbol on the column instead.

I can’t find the key symbol – where is it? Look on the plastic shroud around the steering column, usually the right-hand face. It is a small embossed key outline and is easy to miss until you know it is there.

The blade unlocked the door but the alarm is blaring – is that a fault? No. Mechanical unlocking bypasses the remote, so the alarm arms briefly; it silences the instant the immobiliser reads your key.

Held the fob to the column and still no start – what next? Reposition the fob and retry. If the car is completely dead or only clicks, the cause is more likely the X3’s 12 V battery than the fob.

Which battery does the G01 fob use? A single CR2032 3 V lithium coin cell. Hold it by the edges when fitting it.

If a warning light stayed lit after the key trouble, you can look up its meaning on our sister site autodtcs.com.