Inhibition Proximity Switch Signal Failure on Channel A

TASK 78-31-00-810-940-A
Inhibition Proximity Switch Signal Failure on Channel A

1. Possible Causes

HCU-T/R, ENG1 [4310EG1]
HCU-T/R, ENG2 [4310EG2]
HARNESS-FAN, WF02 [4218KS]
HCU PROXI SENSOR ENG 1A [100EG1]
HCU PROXI SENSOR ENG 2A [100EG2]
[4000KS]

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

REFERENCE	QTY	DESIGNATION
No specific	1	PLIERS - JAWED, SOFT

B. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 71-00-00-810-843-A	Nacelle Component and Harness Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
AMM 71-13-00-010-802	Opening of the Fan Cowl Doors
AMM 71-13-00-410-802	Closing of the Fan Cowl Doors
AWM 715135
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 73-21-62-000-802	Removal of the EEC Wiring Harness (WF02)
AMM 73-21-62-400-802	Installation of the EEC Wiring Harness (WF02)
AMM 78-31-00-210-802	General Visual Inspection (GVI) of the Proximity Sensor Targets
AMM 78-31-00-710-805	Operational Test of Thrust Reverser with MCDU
AMM 78-31-01-000-801	Removal of the TRAS Hydraulic Control Unit (HCU)
AMM 78-31-01-400-801	Installation of the TRAS Hydraulic Control Unit (HCU)
AMM 78-31-22-000-801	Removal of the Hydraulic Control Unit (HCU) Proximity Sensor
AMM 78-31-22-400-801	Installation of the Hydraulic Control Unit (HCU) Proximity Sensor
FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 783611
FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 783612

3. Fault Confirmation
Subtask 78-31-00-710-256-A ** ON A/C NOT FOR ALL

A. Do the operational test of the thrust reverser with the MCDU to confirm this fault AMM 78-31-00-710-805.
(1) If the maintenance message does not come back, troubleshoot as described in the nacelle component and harness troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-843).
(a) Monitor the engine 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.

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 78-31-00-810-285-A ** ON A/C NOT FOR ALL

A. If there is confirmation of the fault:
(1) Get access to the HCU, EEC and pylon junction box.
(a) Remove the access panel from the pylon to get access to the HCU:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL
(b) Open the fan cowl doors AMM 71-13-00-010-802.
(2) At switch (100EG), make sure that the target is not missing and do a visual inspection of the target for bend, breakage or damage AMM 78-31-00-210-802.
(a) If you find a bend, breakage or other damage, or if the target is missing:
1 Replace HCU-T/R, ENG1 [4310EG1] or HCU-T/R, ENG2 [4310EG2] AMM 78-31-01-000-801 and AMM 78-31-01-400-801.
2 Do the test given in Para. 3.
(3) If you find no damage or if the fault continues:
(a) Check for the correct engagement of connector (100EG-A) and proximity sensor (100EG):
1 Repair as necessary.
2 Do the test given in Para. 3.
(4) If check is OK or if the fault continues, use a PLIERS - JAWED, SOFT to disconnect connector (100EG-A) and do a visual inspection of the connector for bent pins, contamination or corrosion or other signs of damage.
(a) If you find damage, replace the pylon harness:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)

AWM 783611

2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)

AWM 783612

(b) Reconnect connector (100EG-A).
(c) Do the test given in Para. 3.
(5) If you find no damage or if the fault continues, disconnect connectors (100EG-A) and P1 from the EEC (4000KS) AWM 715135.
(a) Do a continuity check (less than 5 ohms) between the pins of connectors P1 and (100EG-A) as follows:

Pin N and pin 2
Pin k and pin 5
Pin m and pin 3.

(b) If there is no continuity, disconnect connector (P402) at pylon junction box.
(c) Do a continuity check (less than 5 ohms) between the pins of connectors P1 and (P402) as follows:

Pin N and pin 7
Pin k and pin 8
Pin m and pin 9.

(d) Do a check of each wire for wire-to-wire short circuit and short to ground.
(e) If you find a fault:
1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802.
2 Do the test given in Para. 3.
(f) If there is continuity:
1 Replace the pylon harness:
a FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)

AWM 783611

b FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)

AWM 783612

2 Reconnect all connectors.
3 Do the test given in Para. 3.
(6) If you find no damage or if the fault continues:
(a) Replace HCU PROXI SENSOR ENG 1A [100EG1] or HCU PROXI SENSOR ENG 2A [100EG2] AMM 78-31-22-000-801 and AMM 78-31-22-400-801.
(b) Do the test given in Para. 3.
(7) If you find no fault or if the fault continues, replace [4000KS] AMM 73-21-01-000-801 and AMM 73-21-01-400-801.
(a) Do the test given in Para. 3.

5. Close-up
Subtask 78-31-00-860-050-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 fan cowl doors AMM 71-13-00-410-802.
(b) Close the pylon access panel:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
413AL
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
423AL

[Rev.8 from Aug 2018] 2026.04.04 04:38:11 UTC