As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AIRCRAFT DEPARTED AND PILOTS NOTICED RT PROPELLER WOULD NOT INCREASE PAST 1900 RPM. TAKE-OFF RPM IS 2000 RPM. IN THE CLIMB IT WAS DECIDED THEY RETURN THE ACFT BACK TO DEPARTURE. TROUBLESHOT AND FOUND THAT THE RT ENGINE OVERSPEED GOVERNER, AIRFRAME COMPONENT WAS AT FAULT AND WAS STUCK IN "TEST" MODE. OVERSPEED GOVERNER REPLACED AND NO FUTHER FAULTS.