What was found
APU FAULT LIGHT ON AFTER START RAN CHECKLIST RESTART GOT FAULT ALSO. GROUNDED - YES. FAULT HISTORY SHOWED 2 NO APU ROTATION SHUTDOWN, MAINT MSG 49-41012. ATTEMPTED START, APU WOULD NOT START. 49-41012 MSG SHOWED. T/S REF B737-900 FIM 49-40 TASK 803. SUSPECT STARTER/ GENERATOR. ACCOMPLISHED B737-900 FIM 49-40 TASK 803 STEP (E)(F) 1-5. NO HELP. REMOVED AND REPLACED STARTER GENERATOR REF B737-900 AMM 49-41-21. APU TURNS FREELY. REMOVED AND REPLACED START CONVERTER UNIT REF AMM 49-41-61 AND START POWER UNIT REF AMM 49-41-71. BOTH BOXES OP CHECK GOOD, APU STARTS NORMALLY, BITE CHECK CLEAR. ETOPS GROUND VERIFICATION SUCCESSFUL.