does anybody know what engine fault code p1531 is

P1531 is your air con linear pressure sensor going out of limits.

A bad electrical contact at the sensor or a voltage problem will fire up that warning too
I'd either clear the code and see if it reappears or get in there and clean up the contacts.
If you still have a problem then there's a few voltage tests you can do to see what's happening there

thanks for the info even the fiat dealer couldnt help