As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU STARTS FINE BUT SHOWS NO VOLTS OR FREQUENCY AND WON'T COME ONLINE TO POWER THE GENERATOR BUSSES. ACFT GROUNDED. PERFORMED CONTINUITY CHECK ON PIN 15 AND PIN 16 ON D48080J CONNECTOR FROM REMOTE APU FIRE CONTROL PANEL. CHECKS GOOD, IAW FIM 24-21 TASK 820. REMOVED AND REPLACED APU GCU G14. OPS CHECK GOOD, IAW AMM 24-21-81. PERFORMED APU START AND SUPPLIED APU GEN ELECTRICAL LOAD. OPS TEST GOOD, IAW AMM 49-11-00.