What was found
"B" AUTOPILOT (NR 2) WILL NOT STAY ENGAGED. GROUNDED-YES. PERFORMED DFCS B FAULT REVIEW FOR A/P DISCONNECTS. LEG 5 SHOWS 1 OCCURRENCE OF 22-11149 - LNAV ENG AIL ACT PRESS LCL INV/ LRU:AIL PRESS SW-2, LEG 9 SHOWS SAME/3 OCCURRENCES. NO OTHER DISCONNECT FAULTS PRESENT. REMOVED AND REPLACED AILERON AUTOPILOT ACTUATOR-B HYDRAULIC PRESSURE SWITCH, REF B737-900 FIM 22-13 TASK 805 AND B737-900 AMM 22-11-40. ALL TESTS PASS. ETOPS SIGNIFICANT SYSTEM GROUND VERIFICATION SUCCESSFUL. PERFORMED LAND VERIFY TEST AND HGS SYSTEM TEST TO RESTART 30 DAY IN USE, REF AMM 22-00-01-730-807 AND 808. ALL TESTS PASS. APPROACH SURVEY ACCOMPLISHED/TRAX.