PEUGEOT 308 Handbook page 114

Driving
Anti-theft protection
Electronic engine immobiliser
The keys contain an electronic chip which has
a secret code. When the ignition is switched
on, this code must be recognised in order for
starting to be possible.
This electronic engine immobiliser locks the
engine management system a few minutes
after the ignition is switched off and prevents
starting of the engine by anyone who does not
have the key.
In the event of a malfunction, you are informed
by a message in the instrument panel screen.
In this case, your vehicle does not start; contact
a PEUGEOT dealer as soon as possible.
112
For reasons of safety and theft
protection, do not leave your electronic
key in the vehicle, even when you are
close to it.
It is recommended that you keep it on
your person: in a pocket, bag, ...