What was found
AFTER LANDING ENG #1 FILTER BY-PASS LIGHT ILLUMINATED. GROUNDED - YES. RELEASED PER MEL 73-4B #1 ENGINE FUEL FILTER DIFFERENTIAL WARNING SYSTEM INOP. DRAINED FUEL FROM FILTER HOUSING NO GROSS CONTAMINATION NOTED PER B737-800 AMM 73-11-02-400-801 FUEL FILTER NOT CLOGGED REQUIRES REPLACEMENT AT NEXT STATION. LEAK CHECK ACCOMPLISHED WITH NO ACTIVE LK NOTICED. ACCOMPLISHED EEC BITE PER B737-800 FIM 73-00 TASK 801 NO FAULT FOUND. REMOVED AND REPLACED #1 ENG FUEL FILTER ASSY REF B737-800 AMM 73-11-01-01 OPS AND LEAK CHECK NORMAL.