As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NO APU GEN AFTER GROUND START. APU FIELD LIGHT ON REAR PANEL. FOUND BPCU FAULTS "SHORTED PMG TRIP" AND "GEN-FIELD WIRING-GCU". REPLACED APU GCU, NO HELP. FOUND WIRE BETWEEN D264C PIN 4 AND D4040P PIN 4 OPEN. REPLACED APUC. CHECKED CONTINUITY FROM APU GEN D316 THROUGH OUT E2-4 SHELF M143 PMG HARNESS, FOUND CONNECTOR D4074J LOOSE. SECURED CONNECTOR. ACCOMPLISHED SUCCESSFUL APU GENERATOR OPERATIONAL CHECK.