As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GUM - FLT 977 - NR 2 OMEGA WARNING LIGHT ON AND DISPLAY BLANK. RESET CIRCUIT BREAKER, WORKED FOR 15 MINUTES, THEN SAME. AIR RETURN BACK TO GUAM AFTER DUMPING 9,000 POUNDS OF FUEL. MAINTENANCE REPLACED NR 2 OMEGA CDU AND RPU, WITH NO HELP. FURTHER TROUBLESHOOTING FOUND PROBLEM WITH NR 2 CDI ASSEMBLY. REMOVED AND REPLACED NR 2 CDI, AND SYSTEM OPERATION CHECK GOOD. (X)