Max tunes 3 Error 20

[Sean14]

Hi , hoping someone can help me with this issue as Im at a loss now, Im getting this E20 on boot and game won’t get past this screen, have swapped the FFB pcb with a known work ing one and still the same , have replaced the steering POT with I think is a good one , large fuse at the Board is good and there is 100V going Into the board and the 5/12Vdc , swapped JVS pcb , could have this be an issue with the PC or the serial card inside it ? Thanks In advance