What was found
(CAN) ON APPROACH, CREW RECEIVED A FLAP FAIL CAUTION MESSAGE WHEN THEY ATTEMPTED TO EXTEND FLAPS. THE FLAPS FAILED AT ZERO DEGREES. CREW CARRIED OUT AN UNEVENTFUL FLAP ZERO LANDING. FAILURE CODES FROM THE FECU INDICATED A FLAP PDU AT FAULT. FLAP DRIVES WERE CLEANED AND RE-GREASED AND THE FLAP PDU (P/N 865D100-7, S/N 110) WAS REPLACED. SKEW DETECTION UNIT WAS RESET AND FLAP OPS CHECKS CARRIED OUT. THE ACFT WAS RELEASED TO SERVICE.