Start the Car With a Dead Key Fob Battery

Last updated: June 12, 2026

The Suzuki SX4 S-Cross (Mk2/JY facelift, 2021–Present) ships with Suzuki’s keyless smart entry and a START/STOP button across most UK and European trims, with a built-in emergency blade in the fob. When the smart fob’s coin cell dies the remote-lock and proximity functions stop, but the immobiliser still reads the key — you start the car by holding the fob against the START/STOP button.

Start the S-Cross Mk2 with a dead fob

1. Unlock and get into the car with the emergency blade first (next section), sit in the driver’s seat and close the door.
2. Press and hold the brake pedal with the selector in N (manual) or P (auto).
3. Hold the flat back of the smart fob directly against the START/STOP button — the button has a short-range back-up coil that reads the fob when its battery is too weak to broadcast.
4. With the fob still touching the button, press the START/STOP button. The engine starts.
5. If it does not catch first time, press the fob flush to the button and try again — a nearly-flat cell needs the fob touching the switch.

Unlock the S-Cross Mk2 with the emergency key blade

1. Slide the release catch on the back of the smart fob and pull the metal blade out of the body.
2. Insert the blade into the lock barrel in the driver’s door handle and turn to unlock. On some trims a small cap covers the barrel — lever it off with the blade tip first.
3. The alarm may sound until you start the engine; running the car clears it.

Immobiliser note

The S-Cross immobiliser reads a passive RFID transponder in the key, not the fob’s battery. The START/STOP button houses the back-up reader, powered by the car, so the engine authorises even with a completely dead fob. As a self-charging hybrid, the S-Cross Mk2 also relies on a small 12V battery for the keyless and immobiliser systems — if that 12V battery is flat as well, the car will not wake regardless of the fob; jump or charge the 12V first. A key warning that stays lit after starting points to a genuine fault rather than a flat cell.

Replace the fob battery

The S-Cross Mk2 smart fob uses one CR2032 3V lithium coin cell. Slide out the emergency blade, then prise the case halves apart at the seam — a fingernail or thin flat tool in the gap is enough. Swap the cell + side up, snap the case shut and refit the blade. Remote locking and proximity entry return at once.

Frequently Asked Questions

Where do I hold the fob to start the S-Cross Mk2?

Directly against the START/STOP button. There is no key slot or column reader — the back-up coil is built into the button.

The car is a hybrid — does that change the dead-fob start?

No. The hybrid drivetrain does not affect the key system. The only difference is that the 12V battery must have charge for the keyless system to wake; if it is also flat, sort the 12V first.

Which battery does the S-Cross Mk2 fob take?

One CR2032 coin cell, sold in any supermarket or hardware shop.

Do I need a workshop tool to start it with a dead fob?

No. The fob-against-button method is a built-in owner procedure; no diagnostic tool is required.

Why did the alarm sound when I used the blade?

Manual entry registers as a possible break-in until the transponder is verified. Starting the engine cancels the alarm.

If a dashboard warning light stayed on after the no-start, look it up on autodtcs.com to confirm it was just the fob and not an immobiliser code.