Renault Scenic 2 (1.9 dci) engine does not start

Hello Community, my question refers to the Renault Scenic 2 (2004 / 1,9 dci). When starting the starter does not turn, the fan goes on and error messages like: oil pressure loss / steering wheel lock / electronic hand brake and alternator broken. After several attempts the car starts. After further short start attempts it also starts again. After a short wait the error picture appears again, as described at the beginning. As long as the valve at the high pressure pu If the valve is no longer powered, then it will only start again after several attempts at starting. The UPC (the safety/– and switching unit) has already been changed, but the damage image is the same. Do you have some ideas or experiences for this problem? I would be very pleased about suggestions. Thank you for your efforts.