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 AD27-05 2L. R & R LT BPSU IAW AMM 27-51-10. OPS CHECK GOOD, COULD NOT DUPLICATE, ACFT OK FOR SERVICE.