Disagree between the N1 Indication and the ECU Output on Engine 1

TASK 77-00-00-810-827-A
Disagree between the N1 Indication and the ECU Output on Engine 1

1. Possible Causes

SENSOR-N1 ROTATIONAL SPD [4000EV]
J9/J10 harness
HJ9/HJ10 harness

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)

3. Fault Confirmation
Subtask 77-00-00-710-082-A ** ON A/C NOT FOR ALL

A. Test.
(1) Not applicable.

4. Fault Isolation
Subtask 77-00-00-810-066-A ** ON A/C NOT FOR ALL

A. The fault may be triggered with N1 fluctuations or due to defective SENSOR-N1 ROTATIONAL SPD [4000EV] or J9/J10 harness.
(1) Read the scheduled maintenance report or class 3 report and check if the message N1 SNSR, J9, ECU or N1 SNSR, J10, ECU is present.

If either message is present, do the related troubleshooting procedure.

(2) If N1 fluctuations were reported when the warning was triggered, do the applicable troubleshooting procedure for ENG1 N1 fluctuations.

Subtask 77-00-00-810-066-B ** ON A/C NOT FOR ALL

A. The fault may be triggered with N1 fluctuations or due to defective SENSOR-N1 ROTATIONAL SPD [4000EV] or HJ9/HJ10 harness.
(1) Read the scheduled maintenance report or class 3 report and check if the message N1 SNSR, J9, ECU or N1 SNSR, J10, ECU is present.

If either message is present, do the related troubleshooting procedure.

(2) If N1 fluctuations were reported when the warning was triggered, do the applicable troubleshooting procedure for ENG1 N1 fluctuations.

Subtask 77-00-00-710-261-A ** ON A/C NOT FOR ALL

B. Do the operational test of the FADEC on the ground (with engine non motoring) AMM 73-29-00-710-040.
(1) If the test gives the message N1 SNSR, J9, ECU or N1 SNSR, J10, ECU, do the applicable troubleshooting procedure.

[Rev.8 from Aug 2018] 2026.04.04 04:37:31 UTC