As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN CRUISE FLIGHT AUTOPILOT DISENGAGED. 'ATT FAIL' AND 'HDG FAIL' WARNING DISPLAYED ON PFD & MFD. FMS DISPLAYED 'AHRS-1 HEADING FAIL' AND 'AHRS-1 INPUT FAIL'. EMERGENCY WAS DECLARED AND DIVERTED TO ALTERNATE AIRPORT. MAINTENANCE REPLACED THE LEFT AHRS UNIT. AIRCRAFT WAS RETURNED TO SERVICE.