Loss of the Feedback Signal of the N1 Speed Sensor through the Channel A on Engine 1

TASK 77-10-00-810-825-A
Loss of the Feedback Signal of the N1 Speed Sensor through the Channel A on Engine 1

1. Possible Causes

harness J9
ECU [4000KS]
SENSOR-N1 ROTATIONAL SPD [4000EV]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-21-50-000-008	Removal of the J9 Harness
AMM 73-21-50-400-008	Installation of the J9 Harness
AMM 73-21-60-000-001	Removal of the Electronic Control Unit (ECU)
AMM 73-21-60-400-001	Installation of the Electronic Control Unit (ECU)
ASM 732513
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)
AMM 77-11-10-000-001	Removal of the N1 Speed Sensor
AMM 77-11-10-400-001	Installation of the N1 Speed Sensor

3. Fault Confirmation
Subtask 77-10-00-710-098-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the operational test of the FADEC 1A on the ground (with engine non motoring) AMM 73-29-00-710-040.
(2) Read the CLASS 3 FAULT of the FADEC 1A on the MCDU and make a record of the class 3 maintenance message.

4. Fault Isolation
Subtask 77-10-00-810-074-A ** ON A/C NOT FOR ALL

A. If the test of the channel A gives the maintenance message N1 SENS, J10, ECU:

do a check for open or short to ground of the harness J9 between the ECU (4000KS) and the N1 speed sensor ASM 732513.

(1) If the wiring is not correct:

repair the above wiring.

(2) If the wiring is correct:

disconnect the harness J9 from the ECU (4000KS) and do a resistance check of the cable between:
. pins 16 and 17 (40 to 80 ohms)
. pins 16 and 6 (> 10 megohms)
. pin 16 and the ground (> 10 megohms).

(a) If the resistance values are in the specified limits:

replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

(b) If the resistance values are out of the specified limits:

disconnect the harness J9 from the N1 speed sensor and do a resistance check of the sensor between:
. pins 1 and 2 (40 to 80 ohms)
. pins a and 3 (> 10 megohms)
. pin 1 and the ground (> 10 megohms).

1 If the resistance values are in the specified limits:

replace the harness J9 AMM 73-21-50-000-008 and AMM 73-21-50-400-008.

2 If the resistance values are out of the specified limits:

replace the SENSOR-N1 ROTATIONAL SPD [4000EV] AMM 77-11-10-000-001 and AMM 77-11-10-400-001.

Subtask 77-10-00-710-099-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.A.

[Rev.8 from Aug 2018] 2026.04.04 04:37:39 UTC