Start the Car With a Dead Key Fob Battery

Last updated: June 11, 2026

If the remote on your Peugeot 208 (Mk1/A9, 2012–2019) has stopped unlocking the doors, or the dash shows “Key not detected” on a keyless car, the coin cell in your fob has almost certainly died. The good news: a flat fob battery does not strand you. Mk1 208s split into two camps — most have a conventional flip key you turn or insert, while higher trims carry Peugeot’s keyless “Access & Start” with a START/STOP button. Both have a backup.

Work out which one you have. If your key flips a metal blade out at the press of a button and you twist it in the ignition to start, you are on the flip-key system. If there is a permanent push-button on the dash and no ignition barrel, you have keyless Access & Start.

Start the 208 With a Dead Fob

On a keyless Mk1 208, the immobiliser can still read your key at point-blank range through a backup antenna built into the steering column, just to the left of the wheel.

1. Get in first with the emergency blade (next section) — the remote buttons are dead.
2. Sit in, press the brake pedal and keep it down.
3. Hold the flat face of the fob against the steering-column shroud, just left of the steering wheel, where the backup reader sits.
4. With the fob held there, press the START/STOP button. The car powers the passive chip in the key, recognises it and releases the engine.
5. If it does not catch first time, shift the fob a centimetre and press again — the read zone is small.

On a flip-key 208 there is no special trick: the transponder chip in the key head is read by the coil around the ignition barrel, which needs no fob battery. Flip the blade out, insert it and turn as normal — the engine starts even with a flat coin cell. The dead battery only stops the remote buttons working from a distance.

Unlock the 208 With the Emergency Key Blade

1. On a keyless fob, slide the catch and pull the folding metal blade out. On a flip key it is already the blade you use.
2. Go to the driver’s door. The lock barrel on the 208 sits in the door handle; on some trims it is exposed, on others it hides behind a small plastic cap you prise off with the blade tip.
3. Insert the blade and turn to unlock. This frees the driver’s door; the interior locking button releases the rest once you are in.

Why the Immobiliser Still Works

The chip that verifies your key is passive — it draws power by induction from the car’s reader coil, like a contactless card, and never needed the coin cell. The fob battery only feeds the long-range radio for remote locking. That is why touching the fob to the column (keyless) or the blade in the barrel (flip key) still lets the 208 see a valid key.

Replace the Key Fob Battery

1. On the keyless fob, remove the emergency blade first to release the case; on the flip key, undo the small screw or split the case along its seam.
2. Ease the two halves apart with a thin coin or plastic tool.
3. Lift out the old cell. The Mk1 208 keyless fob uses a CR2032; the flip-key remote typically takes a CR1620 — check the marking on the cell you remove.
4. Fit the new battery the same way up, handling it by the edges.
5. Reassemble, refit the blade and test the buttons. A flip-key remote may need a couple of button presses near the car to re-sync.

Frequently Asked Questions

Where do I hold the fob to start a keyless 208? Against the steering-column shroud just left of the wheel, then press START/STOP. That is where the backup antenna lives.

My 208 has a key I turn — will it still start? Yes. The ignition reads the chip in the key head without any fob battery, so it starts normally; only the remote buttons stop working.

Which battery does my 208 fob take? CR2032 for the keyless Access & Start fob, usually CR1620 for the flip-key remote. Confirm by the number on the old cell.

The blade turned but a door stayed locked — why? The blade unlocks the driver’s door only. Open it, get in and use the interior central-locking button to release the others.

It only starts when I hold the fob to the column — is the car faulty? No, that is the flat-battery symptom. Fit a fresh CR2032 and normal keyless starting returns.

If a warning light stayed on afterwards, you can look up what the code means on our sister site autodtcs.com.