hello Martin, could it be that the error message is "fail bus system" if so there is a communication error between display and MPU-board or EPS controller. First control the option setting put RS1 to 6 and go with the Mode button true the menu untill you see fingertip, in your case it must be ON. Second, on the MPU-board there are 4 LED (P15-P6-Hyd-Trv)and diplay board you have 2 LED (P7-Cpu) see witch one is blinking, on or off.
Kind regards
Marc