These instructions apply to the Peugeot 308 Mk3 (P5) 2021-Present. For other models, please choose your vehicle here.
Last updated:
The Peugeot 308 (Mk3/P51, 2021–Present) — hatch, SW estate and plug-in hybrid — comes with Peugeot’s keyless “Access & Start” on most trims. When the fob coin cell dies, the doors stop responding and the START/STOP button shows “key not detected”. It looks like a flat car battery, but it is only the fob. The key still carries a battery-free transponder the 308 can read at point-blank range, so you can unlock and start it.
Base trims with a plain remote and turn ignition aren’t affected for starting — a dead fob only kills the remote buttons; unlock with the blade and turn the key. The steps below are for keyless cars.
Start the keyless Peugeot 308 Mk3 with a dead fob
- Open the car with the emergency blade (next section), sit in the driver’s seat and shut the door so the cabin antenna can search for the key.
- Press and hold the brake pedal — on the plug-in hybrid, the same brake-and-button sequence applies.
- Press the START/STOP button once. The 308’s digital i-Cockpit cluster shows “key not detected”.
- Hold the flat face of the fob against the steering column, just left of the START button, over the backup antenna.
- With the fob held there and the brake pressed, press START/STOP again. The immobiliser reads the passive chip and the car starts, or shows READY on the hybrid.
Unlock the doors with the emergency key blade
- Slide the catch on the fob and withdraw the metal emergency blade.
- Lever off the small cover at the rear of the driver’s door handle with the blade tip to expose the hidden lock cylinder.
- 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 308 Mk3 fob holds a battery-powered radio for hands-free entry and a passive RFID transponder powered wirelessly by the car. A flat CR2032 disables only the radio; the transponder still answers the immobiliser when held against the column antenna. That is the reason the close-range start works even with a dead cell.
Replace the fob battery
The Peugeot 308 Mk3 fob takes a single CR2032 3V lithium coin cell. Remove the emergency blade, split the case halves at the seam, lift the old cell out and fit the new one with the + face up, then clip it shut. A fresh CR2032 lasts two to three years; if keyless range has been dropping, change it before it leaves you holding the fob to the column.
Frequently Asked Questions
Does the 308 plug-in hybrid use the same method? Yes. Hold the fob against the steering column and press START/STOP with the brake down to bring the hybrid to READY.
Where do I hold the fob on the 308 Mk3? Flat against the left of the steering column by the START button. If it doesn’t read first time, nudge the fob a centimetre and press again.
Why is the keyhole hidden on the 308? Peugeot caps the cylinder for a clean handle. Prise the small cover off the end of the driver’s door handle with the blade to reach it.
What battery does the 308 fob use? A CR2032 lithium coin cell, sold anywhere and swapped in minutes.
Is it normal for the alarm to sound when I use the blade? Yes. 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 appeared with the key message, you can decode it on our sister site autodtcs.com.
Disclaimer: The information on this page is provided for general guidance only. Always follow your official service manual and safety precautions when working on your vehicle. We are not responsible for errors, omissions, or any damage resulting from the use of this information.
This website is an independent resource and is not affiliated with, endorsed by, or sponsored by Peugeot. All trademarks and brand names belong to their respective owners.