What was found
TOP OF DESCENT N1'S MATCHED AS THROTTLES RETARDED THROUGH 60% THEN #1 N1 LAGGED BY UPTO 12% AND TOOK ADDITIONAL 20 SECONDS TO REACH IDLE #2 ENG. GROUNDED - YES. VERIFIED FADEC3 SOFTWARE PER B737-900 IPC 73-21-60-01A. FOUND FMV DATA TO BE UNUSUAL DEMAND AND POSITION READ JUST UNDER 6% ON #1 ENG #2 ENG DEMAND AND POSITION READ APPROX 8%. B737-900 FIM 73-05 TASK 816 STEP E 8 REQUIRES HMU REPLACEMENT. REMOVED HMU PER T/C N8473000 AND REINSTALLED HMU PER T/C N8473001. LEAK AND OPS CK GOOD ON #1 HMU. VERIFIED N1'S AT ACCEL AND DECEL WERE MATCHED, OK FOR CONT'D SERVICE.