As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APU START UP, WITH BATTERY VOLTAGE AT 31 VOLTS, APU NO LIGHT OFF. NO ROTATION. APUC MESSAGE RPM BELOW 7% AND AUTO SHUT DOWN. NO BATTERY VOLTAGE DROP WHILE CRANKING. REPLACED APU STARTER PER MM. ALSO REPLACED APUC PER MM. APU STARTED ON FIRST ATTEMPT WITH ALL NORMAL INDICATIONS.