As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING ENGINE GROUND RUN, RN 1 AND 2 HEADING SPLIT 70 DEGREES AND ADAHRS HDG MISCOMPARE FLAG CAME ON. HEADING CAME TO APPROXIMATELY 45 DEGREES BY TIME FOR SHUTDOWN. REPLACED ADAHRS UNIT IAW MM PROCEDURES, AND ACFT RETURNED TO SERVICE.