What was found
OBSERVED #2 MAIN FUEL TANK INCREASE FROM QUANTITY 8.57 TO 8.80 IN CRUISE AFTER FUEL TEMP DROPPED BELOW 0 DEG. FUEL BURNED/ USED READING TAKEN CONSISTENT WITH NO ACTUAL INCREASE IN MAIN TANK FUEL. GROUNDED - YES. ACCOMP FQIS BITE CURRENT STATUS NO FAULTS, NO FLT FAULTS. ACCOMP GROUND TEST, TEST PASS REF B737-900 FIM 28-41 TASK 801. ACCOMP COMPARISON CHECK FOR #2 MAIN TANK, COMPARISON IS WITH IN LIMITS REF B737-900 AMM 28-41-00-720-801.