As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOTHROTTLE DISENGAGED UNCOMMANDED ON DESCENT AND WOULD NOT RE-ENGAGE. ACFT GROUNDED. AUTOTHROTTLES LOGGED FAULT MESSAGE 22-31543, ENG 28 VDC INV, FAULT IS LOGGED IN PREVIOUS A/T DEFECTS. OPS CHECKED THE AUTOTHROTTLE DISCONNECT SWITCHES, NO FAULT NOTED. REMOVED AND REPLACED THE MCP IAW AMM 22-11-34, OPS CHECKED NORMAL. ALL LLM TESTS PASSED.