As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 4503 - WHILE TAXIING FOR TAKEOFF, THE AUTO COARSEN LOW MODE FAILED. AIRCRAFT RETURNED TO THE GATE. MAINTENANCE GROUND RAN AIRCRAFT AND COULD NOT DUPLICATE PROBLEM. THE CTOT PANEL WAS REPLACED AS PRECAUTIONARY MAINTENANCE. (M)