What was found
BOS - FLT 921 - ON CLIMB-OUT FROM BOS, THE NR 1 ENGINE OIL FILTER BYPASS LIGHT ILLUMINATED. ENGINE WAS BROUGHT BACK TO IDLE AND AN EMERGENCY WAS DECLARED. FLIGHT RETURNED TO FIELD AT BOS AND LANDED WITHOUT INCIDENT. THE NR 1 ENGINE WAS SHUT DOWN AFTER LANDING. MAINTENANCE REMOVED AND REPLACED THE NR 1 ENGINE OIL FILTER (P/N 056306-06). NO CONTAMINATION WAS FOUND. REMOVED AND REPLACED THE NR 1 ENGINE OIL FILTER BYPASS SWITCH. RAN ENGINE. OPS CHECK AND LEAK CHECK GOOD. (X)