As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO START APU WHILE TAXI IN. TRIED TWO ATTEMPTS. APU INOP. PERFORMED FIM 49-11FT 987 & 988. FOUND FAULTS WITH THE ECU. PERFORMED FIM 49-11 FAULT TREE 988, FOUND APU BATTERY CHARGER TO BE SUSPECTED AT FAULT. PERFORMED FIM 49-11 FT 988, VERIFIED BATTERY CHARGER AT FAULT. REMOVED AND REPLACED APU BATTERY CHARGER IAW AMM 24-31-05-424-007. REMOVED AND REPLACED THE APU BATTERY IAW AMM 24-31-04-004-001.