As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU AUTO SHUTDOWN. FOUND APU CONTROL UNIT NOT TESTING. REPLACED APU CONTROL UNIT. REPLACED APU STARTER AND APU CRANK RELAY. LATER APU AUTO SHUTDOWN. APU FAULTS DC PWR LOSS.THE NEWLY FITTED CONTROLLER HAD THIS FAULT ON TWO OTHER AIRCRAFT. REPLACED CONTROLLER. SYSTEM TEST AND BITE TEST GOOD.