One of these days when repairing a puncture, I notice thet the rims of my 2002 L322 Td6 Vogue, are equiped with tyre pressure monitor.

I didn't know and in the owners manual there's nothing about it.
Is there a function to monitorize the tyres pressure? And if so, where can be activated?

Cheers

Had these fitted on my old td6 also, wheels would have been off a newer shape i imagine!

Yep - newer cars had them as an option, so can only assume someone put second hand wheels on yours at some point.