A "SYSTEM" diagnostic usually requires a complete initialization of the centrifuge. I previously posted ALL of the steps required to do this for all Beckman Avanti J series centrifuges on this data base. First, however, you need to know which SYSTEM and DRIVE diagnostics you have. Again, I previously posted the necessary steps to download the error codes, too. The drive diagnostic may or may not actually be the drive motor assembly or one of the electronic assemblies. Either way you still need to know what the error codes actually are before proceeding. I worked on them for 17 years before retiring from Beckman Coulter and what I posted is right out of the service manual. Get back to me after you have the codes and we can proceed from there.
Don