What was found
DURING CLIMB, PASSING LOW 20,000 F/O ATTEMPTED TO ENGAGE AUTOPILOT B, WOULD NOT ENGAGE. TRIED AUTOPILOT A, CWSA, CWSB, BOTH MASTERS - NO COMBINATION WOULD WORK. NO WARNING, CAUTIONS OR HORNS RECEIVED. ALL CBS CHECK GOOD. ACFT GROUNDED. DIVERSION TIME - 46 MINUTES. ACCOMPLISHED CHANNEL A AND B DFCS FAULT REVIEW FIM22-11 801, ADIRS LT AND RT BITE FIM34-21 801, SMYD 1 AND 2 BITE FIM27-32 801 AND HGS FAULT REVIEW. ALL 4 SYSTEMS VERIFY AIR DATA ISSUES ON THE LT SIDE ONLY PRIOR TO FLIGHT LEG 5 & 6. NO RELEVANT AIR DATA ISSUES LOGGED IN LAST 5 FLIGHT LEGS. DFCS F.L. 4 SHOWS SEVERAL FAULTS ON BOTH CHANNELS FOR STAB TRIM CUTOUT, 22-11182, 22-11161, 22-11208. FLIGHT LEGS 1 THRU 3 NO OTHER RELEVANT FAULTS. ACCOMPLISHED EXTENDED BITE MAINTENANCE NR 32 SPD/STB TRIM, NR 35 DUAL STAB, STAB TRIM MOTOR TEST REF MM27-41-71, AND STAB TRIM MOTOR TEST REF MM22-11-81. ALL TESTS PASS WITH STAB MOVING SMOOTHLY AT PROPER RATE WITH NO DEFECTS NOTED. ACCOMPLISHED FIM 22-13 813 WITH NO DEFECTS NOTED. REPLACED R384 FOR LIKELIHOOD OF AN INTERMITTENT FAILURE IN THE CUTOUT POSITION INHIBITING BOTH A & B AUTOPILOTS FROM ENGAGING. RE-ACCOMPLISHED EXTENDED MAINTENANCE NR 32 AND NR 35, STAB TRIM MOTOR TEST MM27-41-71 AND MM22-11-81 AS WELL AS DFCS BG 49 LAND VERIFY. ALL TESTS PASS. AUTOTHROTTLE OPS NORMAL REF MM22-31-00. ADDITIONAL LWMP TESTS DFCS LRU REPLACE FOR A/T BG 43. TEST PASS.