What was found
FLAPS FAIL CAUTION MESSAGE WHEN SELECTING FLAPS FROM 0 TO 20 AFTER ENGINE START PERFORMED TROUBLESHOOTING IAW FIM REV 44 IAW AD 2009-06-12 PARA (H)(6)(I) AMOC DATED DECEMBER 07,2012,AND PA AD27-05 2L. R & R LT BPSU IAW AMM 27-51-10. OPC GOOD, COULD NOT DUPLICATE, ACFT OK FOR SVC.