As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATB - PRIMARY FLT AND NAV DISPLAYS BLANKING. C/W TSM 24-00-00 FAULT ISOLATION CH GPCU BITE. GCU FAILED. REMOVED AND REPLACED NR 2 ENGINE GCU REF A300 MM 24-22-12-00. PERFORMED OPERATIONAL TEST REF AMM 24-41-00-05. TESTS OK, OK TO CONTINUE SERVICE.