As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING T/C 7827300 ON #1 ENGINE FOUND FAULT CODE 73-20311, THE START SIGNAL AND ARINC BUS DATA DISAGREE, SHORT TIME FAULT, DEFERRED PER T/C 7827300. GROUNDED - YES. REMOVED AND REPLACED #1 ENGINE ELECTRONIC CONTROL UNIT, REF B737-800 AMM 73-21-60. OPERATIONAL CHECK GOOD. NO FAULTS CURRENTLY POSTED AT THIS TIME. ALL GROUND VERIFICATION TEST SATISFACTORY.