As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENROUTE GOT AN ATC FAULT EICAS MESSAGE. CREW REPORT SYSTEM RECOVERED DURING FLIGHT.TESTING IN PROGRESS. FIM: 34-53 FAULT TREE 803, BOTH ATC TRANSPONDERS TESTED PER FIM TASK34-53. FAULT TREE 803. NO FAULTS SHOWN AND BOTH TESTED SATIS. GREEN LED INDICATED AT EACH TRANSPONDER.