What was found
RETURNED TO HNL DUE TO FAILED EN ROUTE ETOPS VERIFICATION, APU ALTITUDE START. SUPPLEMENTAL DATA UPDATE, THE CAUSE OF THE FAILED ALTITUDE START WAS NOT CONFIRMED. TEST CELL FINDINGS COULD NOT REPEAT NO START EVENT. THE FOLLOWING LRU WERE ROUTED-GENERATOR OIL SWITCH, P2 SENSOR, LOT SWITCH, EXCITER, DE-OIL SOLENOID VALVE, FUEL FLOW DIVIDER, AND FUEL CONTROL UNIT RELATED TO ALTITUDE STARTING WERE REPLACED AS PRECAUTIONARY. APU PASSED THE AS-RECEIVED DIAGNOSTIC TEST. APU WAS TREATED AS A CONVENIENCE SHOP VISIT AND MADE SERVICEABLE. SUBSEQUENT, THE APU AND A/C COMBINATION EXHIBITED SAME EVENT. THE APU CONTROLLER AND APU START SWITCH WAS REPLACED. NO OTHER EVENTS HAVE OCCURRED.