How do you reset the imobiliser on a xsara picaso?

To reset the immobiliser on a Citroën Xsara Picasso, first ensure that you have the correct key fob. Insert the key into the ignition and turn it to the "On" position without starting the engine; leave it there for about 10 minutes until the immobiliser light goes off. Turn the ignition off, then try starting the engine. If the issue persists, it may require diagnostic tools or professional assistance to reset the immobiliser system.