As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT A WILL NOT REMAIN ENGAGED. GROUNDED - YES. PERFORMED DFCS BITE REF B737-900 FIM 22-11 TASK 801. UNDER FAULT HISTORY LEG 1 CH. A FOUND ENGAGE ATTEMPT FAULTS AIL SYNC INV >4 SEC MSG 22-11189 AND AIL ACT PRESS LCL INV MSG 22-11147. REF FIM 22-13 TASK 804 INITIAL EVAL. PERFORMED FIM 22-11 TASK 801 LRU TEST GROUP 31 FOR CH.A AND CH. B. TEST PASS.