What was found
LEFT FUEL TRANSFER: WHILE AT FL400, FUEL CROSSFEED WAS SELECTED FROM L TANK TO R ENG. THE FUEL XFEED AND FUEL BOOST L ANNUNCIATED AS NORMAL. SHORTLY THEREAFTER WE RECEIVED A MASTER CAUTION WITH FUEL BOOST R ANNUCIATOR. THE CROSSFEED WAS THEN SELECTED OFF AND BOTH L AND R FUEL BOOST REMAINED ON. WE THEN ACCOMPLISHED THE QRH FOR FUEL BOOST L OR R. THE BOOST PUMPS WERE SELECTED ON THEN BACK TO NORM POSITION. WE DID THIS SEPERATELY FOR EACH BOOST PUMP AND THE ANNUNCIATORS CLEARED. CORRECTIVE ACTION; PERFORMED SATISFACTORY OPS CHECK OF FUEL TRANSFER SYSTEM. WAS NOT ABLE TO DUPLICATE FAULT. GAINED ACCESS TO AND SWAPPED LEFT AND RIGHT FUEL PCB BOARDS REMOVED AND REPLACED XFEED ACTUATOR. OPS CHECK OK. NO FURTHER DEFECTS NOTED. WORK PERFORMED IN ACCORDANCE WITH CE560XL AMM 28-21-06.