What was found
AUTO PILOT DISENGAGED AT 34000 FT WITH NO PILOT INPUTS. ON DESCENT THE AUTO PILOT KICKED OFF AGAIN WITH OUT ANY PILOT INPUT. GROUNDED - YES. DEFECT DID NOT INDICATE WHICH A/P ENGAGED. USING DFCS FAULT REVIEW DETERMINED B A/P ENGAGED. FAULT MSG 22-11607 ASSOCIATED WITH DISCONNECT AT 34,000FT AND MSG 22-11833 ASSOCIATED WITH DISCONNECT AT 9000FT. T/S PER B737-900 FIM 22-11 TASK 817 AND PER FIM 22-12 TASK 803. PERFORMED MCP TESTS PER FIM 22-11 TASK 803, ALL TESTS PASS. PERFORMED FIM 22-12 TASK 804 FOUND ALL C/B'S SET. PERFORMED DFCS BITE TEST PER FIM 22-11 TASK 801, NO FAULTS. NO PREVIOUS HISTORY, CK'S GOOD FOR SERVICE.