As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT THE GATE AND AFTER STARTING BOTH ENGINES AND REMOVING GROUND POWER, THE FLIGHT CREW REPORTED A STRONG ELECTRICAL / FIRE SMELL. MAINTENANCE INSPECTED ALL ELECTRICAL COMPONETS OF THE AFFECTED SYSTEMS AND PERFORMED GROUND OPERATIONAL CHECKS WITH NO DISCREPANCIES DETECTED. THE AIRCRAFT WAS RETURNED TO SERVICE.