As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
#1 FMC CDU WENT BLANK DURING PDC CHECK AND WILL NOT COME BACK ON, SWAPPED CDU'S AND PROBLEM FOLLOWED, NEED FMC CDU. SWAPPED CDU'S BACK TO ORIGINAL POSITIONS. GROUNDED - YES. REMOVED AND REPLACED #1 FMC CDU IAW AMM 34-61-01/401, GROUND FUNCTIONAL TEST GOOD.