What was found
(CAN) JUST PRIOR TO TOP OF DESCENT, NR 1 ENGINE FUEL FILTER BYPASS LIGHT CAME ON. FUEL FILTER BYPASS CONNECTOR CLEANED AND REINSATLLED IAW AMM 73-34-01. ENGINE RUN C/O IAW 71-00-00 AND NR 1 EEC BITE C/O IAW AMM 73-21-00. NO CURRENT FAULTS AT THIS TIME. ON TAXI OUT FOR NEXT FLIGHT THE BYPASS LIGHT ILLUMINATED AGAIN. AIRCRAFT RETURNED TO GATE. NR 1 ENGINE FUEL FILTER DIFFERENTIAL PRESSURE SWITCH REPLACED IAW AMM 73-34-01. ENGINE RUNS COMPLETED. MRB APPROVED PROGRAM OF SWITCH REPLACEMENT IS IN THE PROCESS OF BEING IMPLEMENTED FOR SWITCHES EXCEEDING 15,000HRS. NO FURTHER ACTION PLANNED FOR THIS OCCURANCE.