What was found
ON PARKING, APU WAS STARTED AND PUT ON THE BUS. IT THEN SHUTDOWN WITH A FAULT LIGHT ILLUMINATED. APU VOLTS & FREQS OK. APU MX HISTORY PAGE SHOWS 99 FAULTS (EVERY APU CYCLE) MSG 49-72103, DATA MEMORY MODULE CIRCUIT FAILURE. ACCOMPLISHED FIM 49-70, TASK 806, VERIFIED P11 AT DMM & D10436 AT APU FIREWALL RECEPTACLE SECURED. TRIED KNOWN GOOD APU ECU M1709, NO HELP, REINSTALLED ORIGINAL APU ECU. CURRENT STATUS PAGE SHOWS MSG 49-72103. FAULT HISTORY PAGE SHOWS 3 FAULTS MSG 49-11019 POWER INTERRUPT, DC POWER LOSS SHUTDOWN. BAT BUS SHOWS 26V, BAT 29V, & AUX BAT 30. REPLACED APU DATA MEMORY MODULE. REF AMM 49-72-11-000-801, 49-72-11-400-801. GROUND VERIFICATION SUCCESSFUL.