What was found
PSEU LIGHT ON. PERFORMED BITE TEST OF PSEU & NO FAULTS NOTED. PILOT STATED THAT LE FLAPS FULL EXT LIGHT OPS NORMALLY DURING PRE-DEPARTURE CHK. BUT DURING TAKEOFF CONFIGURATION, LE FLAPS FULL EXT DID NOT OPS AT ALL & PSEU LIGHT ILLUMINATED. AFTER GATE RETURN, PERFORMED OPS CHK OF FLAPS, LE FLAPS FULL EXT CHK FAILED 2ND TIME. UNABLE TO DUPLICATE PROBLEM. PUT A/C TAKEOFF CONFIG WITH BOTH ENGS RUNNING. LOWERED FLAPS & VERIFIED LE FLAPS FULL EXT LIGHT WORKS. NO PSEU LIGHT CAME ON. PERFORMED PSEU BITE TEST. FLIGHT LEG 0 SHOWS LE FP EX BITE FLT (31-52111) & LE FLAPS EXT FLT (31-52105). ACCOMPLISHED FIM TASK. CONTINUE AT STEP F. REF FIM 32-09 TASK 812, FIM 32-09 TASK 801, AMM 31-51-00. UNABLE TO DUPLICATE PROBLEM.