Hello all,
Update:
I have removed the oil pressure sensor and when I disconnect the electric part, it was leaking oil on the circuity connector. I have put a new sensor on, clean the connector and now the issue is gone. Thanks a lot Gareth for your help. I did not made another pressure test because I assumed that taking into consideration the shape of the old sensor that was the one who caused the error message to appear. Now I did not receive that error message anymore.
Regards.
Eugen