What was found
APU FAULT CAUTION MSG FOLLOWED BY APU FIRE AND BELLS WARNING MSG FOLLOWED BY APU PUMP CAUTION MSG AND THEN APU SHUTDOWN ON ITS OWN. / REMOVED AND REPLACED APU FUEL FILTER IAW CRJ 900 AMM 49-31-03-000/400-801. LEAK CHECK GOOD. NO DEFECTS NOTED. REACTIVATED APU DOOR IAW CRJ 900 AMM 49-14-19-980-801. PERFORMED OPS CHECK OF APU IAW CRJ 900 AMM 49-10-00-866-801. OPS CHECK GOOD, NO DEFECTS NOTED AT THIS TIME.