Engine Position Illegal Channel B

TASK 73-21-00-810-877-A
Engine Position Illegal Channel B

1. Possible Causes

HARNESS-FAN, WF01 [4217KS]
[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 73-21-00-710-806	Test No.7 - EEC Operation Test (Self Test)
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)
AWM 732503
AWM 732504
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 Wiring Harnesses
Pylon Junction Box Connections

3. Fault Confirmation
Subtask 73-21-00-710-128-A ** ON A/C NOT FOR ALL

A. Do the EEC system interactive test to confirm this fault. Refer to FADEC self test AMM 73-21-00-710-806.

NOTE: The Electronic Engine Control (EEC) has detected the engine position discretes for EEC channel B are invalid. The engine position discretes are configured using hardwired jumpers in the pylon wire harness. The EEC is located on the Fan case at the 2 o'clock position adjacent to the Prognostic and Health Monitoring Unit (PHMU).

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).

(1) If the maintenance message does not come back, examine the harness 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.
(2) 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 73-21-00-810-149-A ** ON A/C NOT FOR ALL

A. If there is confirmation of the fault:
(1) Open the thrust reverser cowl-doors AMM 78-36-00-010-802.
(2) Check the circuit for correct jumper configuration in the pylon harness.
(a) Disconnect the electrical connector P407 (407VC-A) from the pylon junction box.
(b) Use the engine position configuration selection table below to continuity check the jumper circuits in the pylon harness for proper configuration. Refer to Table 1.
(c) Check for wire to wire shorts and shorts to ground in the jumper circuits.

Table 1: Engine Position Configuration Selection

Pylon jumper circuit connection, continuity from (407VC-A) pins 19 and 8	Pylon jumper circuit connection, continuity from (407VC-A) pins 20 and 8	Configuration Engine Location
pins 19 and 8 Open	pins 20 and 8 Open	Illegal
pins 19 and 8 Jumpered	pins 20 and 8 Open	Left Engine
pins 19 and 8 Open	pins 20 and 8 Jumpered	Right Engine
pins 19 and 8 Jumpered	pins 20 and 8 Jumpered	Illegal

(d) If a problem is found with the engine position jumper configuration in the pylon harness, repair or replace the pylon harness:

For engine 1 refer to AWM 732503
For engine 2 refer to AWM 732504.

(e) Do the test given in Para. 3.
(3) If the fault continues:
(a) Examine the WF01 (4217KS) harness, connector P2 (4000KS-P2) - EEC (4000KS) and connector P407 (407VC-A) - pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
1 Inspect the harness for damage.
2 Inspect for loose or damaged connector.

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

(b) If a problem is found with the harness or connectors:
1 Replace WF01 HARNESS-FAN(4217KS) AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
2 Do the test given in Para. 3.
(4) If no problems are found with the harness, use a PLIERS - JAWED, SOFT to disconnect the electrical connector P2 (4000KS-P2) from the EEC (4000KS) and connector P407 (407VC-A) from the pylon junction box.
(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 connector P2 (4000KS-P2) to the EEC (4000KS) and connector P407 (407VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(5) If the fault continues:
(a) Disconnect the electrical connector P2 (4000KS-P2) from the EEC (4000KS) and connector P407 (407VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the engine position channel B circuits in the harness. Refer to Table 1. 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: Engine Position Channel B Connector Contacts

WF01 (4217KS) Harness P2 (4000KS-P2) EEC (4000KS) Connector Contacts	WF01 (4217KS) Harness P407 (407VC-A-P407) Pylon Connector Contacts
MM	19
LL	20
PP	8

(b) If a problem is found with the harness or connectors:
1 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
2 Do the test given in Para. 3.
(c) If no problems are found with the WF01 harness, re-connect the connector P407 (407VC-A) at the pylon disconnect.
(6) 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 73-21-00-860-069-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 04:36:40 UTC