As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DC FAIL LIGHT ILLUMINATES ON & OFF ON MODE SELECT UNIT DURING & AFTER ALIGNMENT. ACFT GROUNDED. NO FAULT CODE ON IRS BITE EVEN WITH DC FAIL LIGHT ON. ACCOMPLISHED FIM 34-21 TASK 842 POWER & CONTINUITY CHECKED NORMAL. R & R IFSAU REF AMM 22-11-37. ACCOMPLISHED INSTALLATION TEST FOR ADIRU & IFSAU REF SAME. TESTS PASSED.