As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI, THE ACFT HAD A LOUD AIR NOISE IN THE COCKPIT AND STRONG ELECTRICAL ODOR, VENT EXTRACT FAN FAULTED. FLIGHT RETURNED TO GATE. THE AIRCRAFT WAS GROUNDED. FOUND EXTRACT FAN TO BE FAULTY. REPLACED EXTRACT FAN IAW MM 21-26-51-400. SYSTEM OPS CHECKED GOOD.