What was found
(CAN) DURING TAKEOFF THE #2 ENGINE RPM BEGAN TO OSCILLATE. THE ENGINE COMPUTER WAS SELECTED TO THE OFF POSITION. THE ENGINE RPM STABILIZED BUT WOULD NOT MAKE POWER, APPROXIMATELY 80 PERCENT N1. THE AIRCRAFT RETURNED TO BASE AND LANDED WITHOUT INCIDENT. TROUBLESHOOTING FOUND THE PT2 SENSOR PROBE TO BE THE FAULT, ALTHOUGH NO DAMAGE TO THE PROBE WAS EVIDENT. THE PROBE WAS REPLACED AND THE ENGINE GROUND RUN WITH THE COMPUTERS ON AND OFF CARRIED OUT. ALL PARAMETERS NORMAL AND THE AIRCRAFT RETURNED TO SERVICE.