As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON POWERING UP FOR TAKEOFF, THE PILOT AND MEDICAL CREW SMELLED NOXIOUS FUMES IN THE CABIN. AFTER INSPECTION IT WAS DETERMINED THAT THE EHSI INDICATOR HAD INTERNAL FAILURE. THE ITEM WAS PLACED ON THE DDL, MEL LIST, THE ACFT WAS FLOWN TO AUROR AND A REPLACEMENT EHSI WAS INSTALLED.