As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING T/C 78273000, #1 ENG SHOWS SHORT TIME FAULT MSG 73-21281. EEC TEST SHOWS CHANNEL A INOP ON BOTH NORMAL AND ALT MODE. DURING FIM 73-27 TASK 805 EEC SHOWED INTERNAL FAULT MSG 73-20101. #1 ENG REQ EEC REPLACEMENT. GROUNDED - YES. REMOVED AND REPLACED #1 ENGING EEC IAW B737-800 AMM 73-21-60/401. OPS CHECK GOOD.