Start the Car With a Dead Key Fob Battery

Last updated: June 12, 2026

The Peugeot 208 (Mk2/P21, 2019–Present) — including the all-electric e-208 — offers Peugeot’s keyless “Access & Start” on mid and high trims. When the fob coin cell dies, the doors stop responding to your hand and the START/STOP button shows “key not detected”. It looks like a flat car battery, but it is just the fob. The key still holds a battery-free transponder the 208 can read at close range, so you can get in and start it.

Entry-level 208s with a plain remote and a turn ignition are unaffected for starting: a dead fob only kills the remote buttons. Use the blade to unlock and turn the key as normal. The steps below are for the keyless car.

Start the keyless Peugeot 208 Mk2 with a dead fob

1. Get in with the emergency blade (next section), sit down and close the driver’s door so the interior antenna can sweep for the key.
2. Press and hold the brake pedal; on the e-208 keep your foot on it as you would on the petrol car.
3. Press the START/STOP button once. The digital i-Cockpit cluster shows “key not detected”.
4. Hold the flat face of the fob against the steering column, just to the left of the START button, where the backup antenna sits.
5. With the fob held there and the brake pressed, press START/STOP again. The car energises the passive chip, recognises the key and starts (or powers up “READY” on the e-208).

Unlock the doors with the emergency key blade

1. Slide the catch on the fob and withdraw the metal emergency blade.
2. On the driver’s door handle, prise off the small cover at the rear end of the handle with the blade tip to expose the hidden lock cylinder.
3. Insert the blade, turn to unlock, then refit the cover. The alarm may sound until the car reads the key and starts.

Why this works — the immobiliser note

The 208 Mk2 fob combines a battery-powered keyless radio with a passive RFID transponder that draws its power wirelessly from the car. A flat CR2032 only disables the radio; the transponder still answers the immobiliser when held against the column antenna. That is the whole reason the “hold the fob to the column” method works on a dead battery.

Replace the fob battery

The Peugeot 208 Mk2 fob takes a single CR2032 3V lithium coin cell. Remove the emergency blade, split the two case halves at the seam, lift out the old cell and fit the new one with the + face up. Clip it shut and refit the blade. If keyless range has been getting shorter, that is the cell fading — a fresh CR2032 restores hands-free locking and start.

Frequently Asked Questions

Does this apply to the electric e-208 too? Yes. The e-208 uses the same keyless fob and steering-column antenna; hold the fob to the column and press START/STOP to bring the car to READY.

Where do I hold the fob on the 208 Mk2? Flat against the left of the steering column by the START button. The read zone is small, so nudge the fob a centimetre and retry if it does not catch.

Why is the keyhole hidden? Peugeot caps the cylinder for a cleaner handle. Lever the small cover off the end of the driver’s door handle with the blade to reach it.

What battery does the fob use? A CR2032 lithium coin cell — the same as most modern Peugeots, available anywhere and swapped in minutes.

The alarm sounded when I opened it — is something wrong? No. Mechanical entry bypasses the alarm by design; it stops as soon as the car recognises the key and you start it.

If a warning light or fault code showed up with the key message, you can decode it on our sister site autodtcs.com.