As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT AC BUS FAILED DURING POWER TRANSFER WHILE SHUTTING OFF ENGINES PERFORMED BITE TEST OF BPCU. LT GCU FAIL AND BTB SW/WIRWEI GCU MESSAGES. REMOVED AND REPLACED LT GCU PER AMM 24-22-02. OPS CHECK GOOD. FOUND LOOSE CONNECTOR J4 AT ELEC SYS CONTROL PANEL. RECONNECTED CONNECTOR. NO FURTHER DEFECTS NOTED.