As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FIELD OFF LIGHT ON AFTER APU REPLACEMENT DURING OPS CHECK. REPLACED APU FUEL CONTROL, NO HELP. APU AUTO SHUTDOWN FAULT LIGHT ON OVERTEMP ECU MESSAGE. MR49305 ON-86 OFF159. TRIED TWO FUEL CONTROL UNITS. SAME RESULT. SWAPPED APU CONTROL UNIT (ECU) AND IGNITION UNIT, NO HELP. RE-INSTALLED ORIGINAL PARTS. APU RAN TO 99 PERCENT THEN SPIKES EGT OVER 780 TEMP AND AUTO SHUTS DOWN. REPLACED APU. APU STARTS AND RUNS.