As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START AND UPON MASTER RECALL MACH TRIM FAIL ILLUMINATED. FAULT LIGHT EXTINGUISHES WITH PUSH TO RESET. GROUNDED - YES. FOUND THE "AFCS A MACH TRIM DC C/B OUT ON THE P18-1 PANEL (C457). INSPECTED C/B & ASSOC WIRING & RESET C/B REF AMM 20-60-01 & WDM 22-18-11 PERFORMED SYSTEM A MACH TRIM LRU TEST REF FIM 22-12 TASK 815 ALL TESTS PASSED.