As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED AN AC ESSENTIAL BUSS CAUTION MESSAGE AFTER TAKEOFF. THE CREW ELECTED TO RETURN TO CLT AND LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE AUTO TRANSFER RELAY IN ACCORDANCE WITH THE ACFT MAINTENANCE MANUAL. OPERATIONAL CHECKS WERE GOOD. ACFT WAS RELEASED FOR SERVICE. (S)