Loss of the Feedback Signal from the FMV Resolver through the Two Channels on Engine 1

TASK 73-29-00-810-854-A
Loss of the Feedback Signal from the FMV Resolver through the Two Channels on Engine 1

1. Possible Causes

HMU-1 [4000KC1]
harness J7
harness J8
ECU [4000KS]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-21-10-000-001	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-000-002	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-001	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-002	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-50-000-006	Removal of J7 Harness
AMM 73-21-50-000-007	Removal of J8 Harness
AMM 73-21-50-000-040	Removal of the HJ7 Harness for SAC Engines
AMM 73-21-50-000-041	Removal of the HJ8 Harness for SAC Engines
AMM 73-21-50-210-001	Visual Inspection of the Wiring Harness
AMM 73-21-50-210-002	Visual Inspection of the Wiring Harnesses
AMM 73-21-50-400-006	Installation of the J7 Harness
AMM 73-21-50-400-007	Installation of the J8 Harness
AMM 73-21-50-400-040	Installation of the HJ7 Harness for SAC Engines
AMM 73-21-50-400-041	Installation of the HJ8 Harness for SAC Engines
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)
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)

3. Fault Confirmation
Subtask 73-29-00-710-124-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the operational test of the FADEC 1A and 1B on the ground (with engine non - motoring) AMM 73-29-00-710-040.

4. Fault Isolation
Subtask 73-29-00-810-146-A ** ON A/C NOT FOR ALL

A. Do this procedure:

NOTE: This fault is generated if one or both FMV resolver signals are out of range, invalid or the signals disagree.

(1) If the test does not give the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU (FMVRES), ECU:

replace the HMU-1 [4000KC1] AMM 73-21-10-000-001 and AMM 73-21-10-400-001.
Visually examine the HMU receptacle and the J7 and J8 harness connectors for damaged pins, contamination and fuel wetting AMM 73-21-50-210-001.

(a) If damage on a connector is found:

replace or repair as required.

(b) If fuel wetting is found:

replace the defective harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006 or the defective harness J8 , AMM 73-21-50-000-007 and AMM 73-21-50-400-007.

no further action is required.

(2) If the test does not give the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU, but are repetitive after the troubleshooting per step 4.A.(1) has been fully done:

replace the ECU [4000KS] , AMM 73-21-60-000-001 and AMM 73-21-60-400-001 (if P/N prefix is 1459M55P, if not proceed to next step).

(a) If the fault continues during the subsequent flights:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

(b) If the fault continues during the subsequent flights:

replace the harness J8 , AMM 73-21-50-000-007 and AMM 73-21-50-400-007.

replace the ECU [4000KS] , AMM 73-21-60-000-001 and AMM 73-21-60-400-001, if not previously replaced.

(3) If the test gives only the maintenance message J7, HMU(FMVRES), ECU (confirmed only on channel A):

disconnect the J7 harness from the HMU receptacle (HMU-A) (located in the left core compartment) and visually examine the J7 harness connector and the HMU receptacle for damaged pins, contamination and fuel wetting AMM 73-21-50-210-001.

(a) If damage on a connector is found:

Replace or repair as required.

(b) If fuel wetting is found:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

Do an electrical resistance test through the HMU receptacle between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 and the ground (> 10 Megohms).

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

replace the HMU-1 [4000KC1] AMM 73-21-10-000-001 and AMM 73-21-10-400-001.

2 If the resistance values are in the specified limits:

reconnect the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006 and continue the troubleshooting.

(d) Disconnect the J7 harness from the ECU (4000KS) receptacle and visually examine the J7 harness connector and the ECU (4000KS) receptacle for damaged pins and contamination AMM 73-21-50-210-001.
1 If damage on a connector is found:

replace or repair as required.

2 If nothing is found:

Do an electrical resistance test through the J7 harness between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 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:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

(4) If the test gives only the maintenance message J8, HMU(FMVRES), ECU (confirmed only on channel B):

disconnect the J8 harness from the HMU receptacle (HMU-B) (located in the left core compartment) and visually examine the J8 harness connector and the HMU receptacle for damaged pins, contamination and fuel wetting AMM 73-21-50-210-001.

(a) If damage on a connector is found:

Replace or repair as required.

(b) If fuel wetting is found:

replace the harness J8 , AMM 73-21-50-000-007 and AMM 73-21-50-400-007.

Do an electrical resistance test through the HMU receptacle between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 and the ground (> 10 Megohms).

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

replace the HMU-1 [4000KC1] AMM 73-21-10-000-001 and AMM 73-21-10-400-001.

2 If the resistance values are in the specified limits:

reconnect the harness J8 , AMM 73-21-50-000-007 and AMM 73-21-50-400-007 and continue the troubleshooting.

(d) Disconnect the J8 harness from the ECU (4000KS) receptacle and visually examine the J8 harness connector and the ECU (4000KS) receptacle for damaged pins and contamination AMM 73-21-50-210-001.
1 If damage on a connector is found:

replace or repair as required.

2 If nothing is found:

Do an electrical resistance test through the J8 harness between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 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:

replace the harness J8 , AMM 73-21-50-000-007 and AMM 73-21-50-400-007.

(5) If the test gives the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU (FMVRES), ECU (confirmed on both channel A and B):

replace the HMU-1 [4000KC1] AMM 73-21-10-000-001 and AMM 73-21-10-400-001 right away for dual channel fault.

(a) If the fault messages repeat:

Do the troubleshooting per steps 4.A.(3) and 4.A.(4).

Subtask 73-29-00-810-146-B ** ON A/C NOT FOR ALL

A. Do this procedure:

NOTE: This fault is generated if one or both FMV resolver signals are out of range, invalid or the signals disagree.

(1) If the test does not give the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU (FMVRES), ECU:

replace the HMU-1 [4000KC1] AMM 73-21-10-000-002 and AMM 73-21-10-400-002.
Visually examine the HMU receptacle and the J7 and J8 harness connectors for damaged pins, contamination and fuel wetting AMM 73-21-50-210-002.

(a) If damage on a connector is found:

replace or repair as required.

(b) If fuel wetting is found:

replace the defective harness J7 , AMM 73-21-50-000-040 and AMM 73-21-50-400-040 or the defective harness J8 , AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

no further action is required.

(2) If the test does not give the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU, but are repetitive after the troubleshooting per step 4.A.(1) has been fully done:

replace the harness J7 , AMM 73-21-50-000-040 and AMM 73-21-50-400-040.

(a) If the fault continues during the subsequent flights:

replace the harness J8 , AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

(b) If the fault continues during the subsequent flights:

replace the ECU [4000KS] , AMM 73-21-60-000-001 and AMM 73-21-60-400-001, if not previously replaced.

(3) If the test gives only the maintenance message J7, HMU(FMVRES), ECU (confirmed only on channel A):

disconnect the J7 harness from the HMU receptacle (HMU-A) (located in the left core compartment) and visually examine the J7 harness connector and the HMU receptacle for damaged pins, contamination and fuel wetting AMM 73-21-50-210-002.

(a) If damage on a connector is found:

Replace or repair as required.

(b) If fuel wetting is found:

replace the harness J7 , AMM 73-21-50-000-040 and AMM 73-21-50-400-040.

Do an electrical resistance test through the HMU receptacle between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 and the ground (> 10 Megohms).

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

replace the HMU-1 [4000KC1] AMM 73-21-10-000-002 and AMM 73-21-10-400-002.

2 If the resistance values are in the specified limits:

reconnect the harness J7 , AMM 73-21-50-000-040 and AMM 73-21-50-400-040 and continue the troubleshooting.

replace or repair as required.

2 If nothing is found:

Do an electrical resistance test through the J7 harness between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 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:

replace the harness J7 , AMM 73-21-50-000-040 and AMM 73-21-50-400-040.

(4) If the test gives only the maintenance message J8, HMU(FMVRES), ECU (confirmed only on channel B):

disconnect the J8 harness from the HMU receptacle (HMU-B) (located in the left core compartment) and visually examine the J8 harness connector and the HMU receptacle for damaged pins, contamination and fuel wetting AMM 73-21-50-210-002.

(a) If damage on a connector is found:

Replace or repair as required.

(b) If fuel wetting is found:

replace the harness J8 , AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

Do an electrical resistance test through the HMU receptacle between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 and the ground (> 10 Megohms).

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

replace the HMU-1 [4000KC1] AMM 73-21-10-000-002 and AMM 73-21-10-400-002.

2 If the resistance values are in the specified limits:

reconnect the harness J8 , AMM 73-21-50-000-041 and AMM 73-21-50-400-041 and continue the troubleshooting.

replace or repair as required.

2 If nothing is found:

Do an electrical resistance test through the J8 harness between:
. pins 16 and 34 (70 to 84 Ohms)
. pins 35 and 36 (21 to 29 or 44 to 76 Ohms)
. pins 18 and 37 (21 to 29 or 44 to 76 Ohms)
. pins 16 and 17 (> 10 Megohms)
. pins 35 and 17 (> 10 Megohms)
. pins 18 and 17 (> 10 Megohms)
. pin 16 and the ground (> 10 Megohms)
. pin 35 and the ground (> 10 Megohms)
. pin 18 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:

replace the harness J8 , AMM 73-21-50-000-041 and AMM 73-21-50-400-041.

(5) If the test gives the maintenance messages J7, HMU (FMVRES), ECU + J8, HMU (FMVRES), ECU (confirmed on both channel A and B):

replace the HMU-1 [4000KC1] AMM 73-21-10-000-002 and AMM 73-21-10-400-002 right away for dual channel fault.

(a) If the fault messages repeat:

Do the troubleshooting per steps 4.A.(3) and 4.A.(4).

Subtask 73-29-00-710-125-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.A.(1).
(1) No additional maintenance action is required if the fault is not confirmed.
(2) Repeat the fault isolation procedure if the fault continues.

[Rev.8 from Aug 2018] 2026.04.04 04:35:57 UTC