What was found
FILTER BYPASS CAUTION ILLUMINATED ON ENGINE NR 1 AFTER ENGINE START UP. ACFT GROUNDED. PERFORMED EEC BITE CHECK FOR NR 1 ENGINE RECENT FAULTS. FOUND FUEL FILTER SIGNALS DISAGREE FAULT MESSAGE PRESENT. CHECKED FUEL FILTER FOR CONTAMINATION IAW AMM 73-11-02. NO CONTAMINATION NOTED. ALL LEAKS CHECKED OK. REMOVED AND REPLACED THE NR 1 ENGINE FUEL FILTER AND O-RINGS WITH NEW. ENGINE IDLE, LEAK CHECKS COMPLETE. NO DEFECTS NOTED IAW AMM 73-11-02.