As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT CREW REPORTED AC ESSENTIAL BUSS CAUTION MESSAGE AND A GENERATOR 1 FAULT IN FLIGHT. CREW RAN QRH AND ATTEMPTED TO START APU WHICH TOOK THREE ATTEMPTS. FLT DIVERTED AND DECLARED EMERGENCY. LANDED SAFELY. REPLACED APU GCU AND K117. OPS CHECKED GOOD.