PHMU N1 and NF Speed Sensor Failure

TASK 77-31-00-810-805-A
PHMU N1 and NF Speed Sensor Failure

1. Possible Causes

HARNESS-FAN, WF01 [4217KS]
HARNESS-FAN, WF02 [4218KS]
PROGNOSTICS AND HEALTH MANAGEMENT UNIT [4609KS]
[4000KS]

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD
No specific	1	PLIERS - JAWED, SOFT

B. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 71-00-00-810-834-A	General Troubleshooting Guidelines for Additional Troubleshooting Information
TSM TASK 71-00-00-810-835-A	Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
AMM 70-70-00-910-803	SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses
AMM 71-00-00-860-814	Shutdown of the Engine
AMM 71-00-00-860-822	Start the Engine (Normal Manual Start)
AMM 71-00-00-860-823	Start the Engine (Normal Automatic Start)
AMM 73-21-01-000-801	Removal of the Electronic Engine Control (EEC)
AMM 73-21-01-400-801	Installation of the Electronic Engine Control (EEC)
AMM 73-21-61-000-802	Removal of the Electronic Engine Control (EEC) Wiring Harness (WF01)
AMM 73-21-61-400-802	Installation of the Electronic Engine Control (EEC) Wiring Harness (WF01)
AMM 73-21-62-000-802	Removal of the EEC Wiring Harness (WF02)
AMM 73-21-62-400-802	Installation of the EEC Wiring Harness (WF02)
AMM 77-31-01-000-801	Removal of the Prognostics and Health Management Unit (PHMU)
AMM 77-31-01-400-801	Installation of the Prognostics and Health Management Unit (PHMU)
AMM 78-36-00-010-802	Opening of the Thrust Reverser Cowl-Doors
AMM 78-36-00-410-802	Closing of the Thrust Reverser Cowl-Doors
EEC and PHMU Wiring Harnesses
PHMU Wiring Schematic

3. Fault Confirmation
Subtask 77-31-00-710-054-A ** ON A/C NOT FOR ALL

A. Do an engine run to idle to confirm repair of this fault AMM 71-00-00-860-822 or AMM 71-00-00-860-823.
(1) Shutdown the engine AMM 71-00-00-860-814.
(2) On the MCDU screen, check if the fault is displayed on the ground scanning report.

NOTE: The Prognostics and Health Management Unit (PHMU) has reported that the N1 (low rotor speed) and NF (fan speed) analog input circuit from the Electronic Engine Control (EEC) have failed. The PHMU is located at the 2 o'clock position on the fan case adjacent to the EEC.

Refer to the general troubleshooting guidelines for additional troubleshooting information (Ref. TSM TASK 71-00-00-810-834).
Refer to the component and harness intermittent troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-835).

(3) If the maintenance message does not come back, examine the harnesses and electrical connectors as described in the component and harness intermittent fault isolation procedure (Ref. TSM TASK 71-00-00-810-835).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(4) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.

4. Fault Isolation

WARNING: BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.

WARNING: REFER TO THE MSDS FOR ALL MATERIAL USED AND THE MANUFACTURER'S SAFETY INSTRUCTIONS FOR ALL EQUIPMENT USED. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.

CAUTION: MAKE SURE YOU REMOVE ELECTRICAL POWER FROM THE EEC BEFORE YOU REMOVE THE ELECTRICAL CONNECTORS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.

Subtask 77-31-00-810-054-A ** ON A/C NOT FOR ALL

A. If maintenance message ENG1D-0750-PHMU N1 AND NF SPEED SNSR FAIL or ENG2D-0750-PHMU N1 AND NF SPEED SNSR FAIL does not come back:
(1) Examine the harnesses and electrical connectors as described in the Component And Harness Intermittent Fault Isolation Procedure.
(a) If you find no damage:
1 Return the engine to service. Monitor the engine for reoccurring maintenance message.
(2) If the maintenance message ENG1D-0750-PHMU N1 AND NF SPEED SNSR FAIL or ENG2D-0750-PHMU N1 AND NF SPEED SNSR FAIL comes back (hard fault):
(a) Perform troubleshooting in the next step.
(3) Open the thrust reverser cowl-doors AMM 78-36-00-010-802.
(4) Examine the WF01 (4217KS) and WF02 (4218KS) harnesses, connectors P1 (4000KS-P1) and P2 (4000KS-P2) - EEC (4000KS), interconnect P103 (4105VC-A)/ J103 (4105VC) and connector P9 (4609KS-P9) - PHMU (4609KS), for problems which are possible between the EEC (4000KS) and the PHMU (4609KS).
(a) Inspect for harness damage.
(b) Inspect for loose or damaged connectors.

NOTE: Loose connectors must be disconnected and examined for further wear or damage.

(c) If a problem is found with the harnesses or connectors:
1 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802, or
2 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
3 Do the test given in Para. 3.
(5) If no problems are found with the harnesses or the fault continues, use a PLIERS - JAWED, SOFT to disconnect the electrical connectors P1 (4000KS-P1) and P2 (4000KS-P2) from the EEC (4000KS), interconnect P103 (4105VC-A)/J103 (4105VC) and connector P9 (4609KS-P9) from the PHMU (4609KS).
(a) Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
(b) Clean the contacts with contact cleaner and clean cloth per SPOP 6. Blow dry with air (at less than 30 psi) across the connector face AMM 70-70-00-910-803.
(c) Reconnect the electrical connectors P1 (4000KS-P1) and P2 (4000KS-P2) to the EEC (4000KS), interconnect P103 (4105VC-A)/J103 (4105VC) and connector P9 (4609KS-P9) to the PHMU (4609KS).
(d) Do the test given in Para. 3.
(6) If the fault continues:
(a) Disconnect the electrical connectors P1 (4000KS-P1) and P2 (4000KS-P2) from the EEC (4000KS), interconnect P103 (4105VC-A)/J103 (4105VC) and connector P9 (4609KS-P9) from the PHMU (4609KS). Use a MULTIMETER - STANDARD to test the PHMU (4609KS) N1 and NF analog input circuits in the harnesses. Refer to Table 1 and Table 2. Look for:
1 Wire-to-wire shorts
2 Shorts to ground
3 Continuity (less than 5 ohms resistance).

NOTE: A short to ground is found when the resistance is less than 100 000 (100K) ohms.

Table 1: EEC to PHMU N1 Analog Input Channel A Connector Contacts

WF02 (4218KS) Harness P1(4000KS-P1) EEC (4000KS) Connector Contacts	WF02 (4218KS) Harness P9(4609KS-P9) PHMU (4609KS) Connector Contacts
W	R
s	P

Table 2: EEC to PHMU NF Analog Input Channel B Connector Contacts

WF01 (4217KS) Harness P2 (4000KS-P2) EEC (4000KS) Connector Contacts	WF01 (4217KS) Harness P103 (4105VC-A) Connector Contacts	WF02 (4218KS) Harness J103 (4105VC) Connector Contacts	WF02 (4218KS) Harness P9 (4609KS-P9) PHMU (4609KS) Connector Contacts
W	6	6	e
s	7	7	d

(b) If a problem is found with the harnesses or connectors:
1 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802, or
2 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
3 Do the test given in Para. 3.
(7) If no problems are found with the harnesses or the fault continues:
(a) Replace PROGNOSTICS AND HEALTH MANAGEMENT UNIT [4609KS] AMM 77-31-01-000-801 and AMM 77-31-01-400-801.
(b) Do the test given in Para. 3.
(8) If the fault continues:
(a) Replace [4000KS] AMM 73-21-01-000-801 and AMM 73-21-01-400-801.
(b) Do the test given in Para. 3.

5. Close-up
Subtask 77-31-00-860-054-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(a) Close the thrust reverser cowl-doors AMM 78-36-00-410-802.

[Rev.8 from Aug 2018] 2026.04.04 04:37:57 UTC