As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU, NO ELECTRICAL AVAILABLE. GROUNDED - YES. BLUE PWR AVAIL LIGHT IS ON BUT NO VOLTS / FREQS SHOWING AND WILL NOT GO ONLINE. SHUT DOWN APU AND CYCLED GCU C/B'S (GCU TESTED NML). APU STARTED AND CAME ONLINE, CKS NML REF B737-900 AMM 24-21-00. GND VERIFICATION SUCCESSFUL.