DOC AIRBUS | TSM A320FTCM Enable Discrete Signal Failure (Single) Channel A
TASK 73-11-00-810-828-A
TCM Enable Discrete Signal Failure (Single) Channel A
1. Possible Causes
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 73-11-00-710-084-A ** ON A/C NOT FOR ALL
Subtask 73-11-00-860-077-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:41:10 UTC
TCM Enable Discrete Signal Failure (Single) Channel A
1. Possible Causes
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 |
| 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 24-41-00-861-002 | Energize the Aircraft Electrical Circuits from the External Power |
| AMM 24-41-00-862-002 | De-energize the Aircraft Electrical Circuits Supplied from the External Power |
| AMM 70-70-00-910-803 | SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses |
| AMM 71-13-00-010-802 | Opening of the Fan Cowl Doors |
| AMM 71-13-00-410-802 | Closing of the Fan Cowl Doors |
| 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) |
| FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1) | |
| AWM 732546 | |
| FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2) | |
| AWM 732547 | |
EEC Wiring HarnessesSubtask 73-11-00-710-084-A ** ON A/C NOT FOR ALL
A. Energize the FADEC of the engine that has a fault report.
(1) Energize the aircraft electrical circuits AMM 24-41-00-861-002.
(2) On the ENG section of maintenance panel 50VU:
(a) Release the FADEC GND PWR/1(2) pushbutton switch (the ON legend comes on).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(5) If the maintenance message comes back (hard fault) in channel A, go to the Para. Fault Isolation.
4. Fault Isolation(1) Energize the aircraft electrical circuits AMM 24-41-00-861-002.
(2) On the ENG section of maintenance panel 50VU:
(a) Release the FADEC GND PWR/1(2) pushbutton switch (the ON legend comes on).
NOTE: After the FADEC is energized, wait ten seconds before you start the test. If you do not wait ten seconds, the interactive mode stops the EEC self-test and this can cause spurious faults.
(3) On Multipurpose Control and Display Unit (MCDU) screen, check if the fault is displayed on ground scanning report. NOTE: The Electronic Engine Control (EEC) has detected the Throttle Control Malfunction (TCM) discrete circuit is out of range or rate in channel A.
(4) 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). - 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).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(5) If the maintenance message comes back (hard fault) in channel A, go to the Para. 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 73-11-00-810-077-A ** ON A/C NOT FOR ALL A. If there is confirmation of the fault:
(1) Open the fan cowl doors AMM 71-13-00-010-802.
(2) Examine the WF02 (4218KS) harness, connector P1 (4000KS-P1) - EEC (4000KS) and connector P402 (402VC-A) - Pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
(a) Inspect for harness damage.
(b) Inspect for loose or damaged connectors.
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.
(3) If no problems are found with the harness or the fault continues, use a PLIERS - JAWED, SOFT to disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P402 (402VC-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 P1 (4000KS-P1) to the EEC (4000KS) and connector P402 (402VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P402 (402VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the the TCM discrete 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).
(b) If a problem is found with the harness or connectors:
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.
(5) If no problems are found with the harness or the fault continues, check Aircraft (A/C) relay and wiring.
(a) In the avionics compartment on the shelf 83VU:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
a Replace the relay 79CE1.
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
a Replace the relay 79CE2.
3 Do the test given in Para. 3.
(6) If the fault continues:
(a) Check the A/C wiring:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
a Remove the relay 79CE1.
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
a Remove the relay 79CE2.
3 Do a check for continuity between pins B and C.
4 Do a check for short to ground and wire-to-wire short at pins 4 and 6.
5 Put a shunt between pins 4 and 6.
6 At pylon junction box, disconnect connector 402VC-A.
7 At 402VC, do a check for continuity between pins 1 and 2.
8 Repair or replace the A/C wiring as necessary:
a FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 732546.
b FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 732547.
9 Remove the shunt and connect 402VC-A and relay 79CE1(2).
10 Do the test given in Para. 3.
(7) If no problems are found with the A/C relay or wiring or the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
5. Close-up(1) Open the fan cowl doors AMM 71-13-00-010-802.
(2) Examine the WF02 (4218KS) harness, connector P1 (4000KS-P1) - EEC (4000KS) and connector P402 (402VC-A) - Pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
(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 harness or connectors: 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.
(3) If no problems are found with the harness or the fault continues, use a PLIERS - JAWED, SOFT to disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P402 (402VC-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 P1 (4000KS-P1) to the EEC (4000KS) and connector P402 (402VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connector P1 (4000KS-P1) from the EEC (4000KS) and connector P402 (402VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the the TCM discrete 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: TCM Discrete Channel A Connector Contacts | WF02 (4218KS) Harness P1 (4000KS-P1) EEC (4000KS) Connector Contacts | WF02 (4218KS) Harness P402 (402VC-A) Pylon Junction Box Connector Contacts |
|---|---|
| T | 1 |
| S | 2 |
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.
(5) If no problems are found with the harness or the fault continues, check Aircraft (A/C) relay and wiring.
(a) In the avionics compartment on the shelf 83VU:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
a Replace the relay 79CE1.
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
a Replace the relay 79CE2.
3 Do the test given in Para. 3.
(6) If the fault continues:
(a) Check the A/C wiring:
1 FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
a Remove the relay 79CE1.
2 FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
a Remove the relay 79CE2.
3 Do a check for continuity between pins B and C.
4 Do a check for short to ground and wire-to-wire short at pins 4 and 6.
5 Put a shunt between pins 4 and 6.
6 At pylon junction box, disconnect connector 402VC-A.
7 At 402VC, do a check for continuity between pins 1 and 2.
8 Repair or replace the A/C wiring as necessary:
a FOR [4020KM1] (POWER PLANT-DEMOUNTABLE, ENG 1)
AWM 732546.
b FOR [4020KM2] (POWER PLANT-DEMOUNTABLE, ENG 2)
AWM 732547.
9 Remove the shunt and connect 402VC-A and relay 79CE1(2).
10 Do the test given in Para. 3.
(7) If no problems are found with the A/C relay or wiring or the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
Subtask 73-11-00-860-077-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) De-energize the aircraft electrical circuits AMM 24-41-00-862-002.
(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) De-energize the aircraft electrical circuits AMM 24-41-00-862-002.