43' Tiara With cummins diesels sat for a few weeks with dead batteries and now no rea

[Sapphire]

43' Tiara With cummins diesels sat for a few weeks with dead batteries and now no reading om oil pressure, rpms, fuel level and others what could be wrong  no engine data

Assuming batteries are now fully charged and holding voltage, I suggest disconnecting (or turning off battery selector) for a few minutes and then reconnecting.  This should "reset" all systems and may correct your issue.  Make sure both house and starting batteries are off or disconnected as either could be feeding different portions of the network.  Hope this helps.