What was found
APU BLEED AIR INOPERATIVE. TRY APU SHUTDOWN & ON BUT SAME CONDITION, SO PNEUMATIC SYS IS DEFERRED IAW MEL 49-11-01-01 CAT C. APU ECU REPLACED IAW AMM 49-61-05, BITE CHECK CARRIED OUT OK. APU PNEUMATICS FUNCTIONALLY CHECKED SERVICEABLE, DUCT PRESS 38 PSI DURING ENG SPIN. THIS CLEARS DMI 50476.