I wouldn`t worry about it. I believe the owners manual states anything between 1- 3 bars with a warm motor is normal. 1 bar at idle is fine, won`t cause any damage, as long as (as Joesph stated) it jumps to 3 bar above idle. Mine stays close to 3 bar at idle and if I get it really hot will range between 2 -3 bar.
Possible cause for a low pressure at idle??? Could range from something as simple as a leaky seal at the oil pickup tube in the pan, bad ground at the instrument cluster to worn main bearings.