DOC AIRBUS | TSM A320FTCM Protection on Ground Always Armed
TASK 73-00-00-810-940-A
TCM Protection on Ground Always Armed
1. Possible Causes
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 73-00-00-710-380-A ** ON A/C NOT FOR ALL
Subtask 73-00-00-860-217-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:36:10 UTC
TCM Protection on Ground Always Armed
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 |
| AWM 279296 | |
| AWM 279297 | |
| AMM 70-70-00-910-803 | SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses |
| AMM 71-00-00-710-806 | Power Assurance 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) |
| 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) |
| AWM 732546 | |
| AWM 732547 | |
| AWM 732548 | |
| AWM 732549 | |
| 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 HarnessesSubtask 73-00-00-710-380-A ** ON A/C NOT FOR ALL
A. Do an engine run to 35 percent N1 to confirm this fault. Refer to power assurance test AMM 71-00-00-710-806.
(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 IsolationNOTE: The Electronic Engine Control (EEC) has detected that the Thrust Control Malfunction (TCM) discrete signal from the aircraft Spoiler and Elevator Computer (SEC) is failed closed. This indicates that the TCM protection on ground is always armed, even when the throttle lever is above a specified throttle lever angle position where TCM protection on ground should be disabled.
(1) 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.
(2) If the maintenance message comes back (hard fault), 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 73-00-00-810-294-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) In 83VU for fault on ENG1 and 84VU for fault on ENG2, replace relays:
(a) If fault is on ENG 1, replace relays 76CE1 and 79CE1.
(b) If fault is on ENG 2, replace Relays 76CE2 and 79CE2.
(c) Do the test given in Para. 3.
(3) If the fault continues:
(a) Remove relays 79CE.
1 Check for 28 VDC at pin X on VU side of 79CE.
a If there is 28 VDC, remove relay 76CE.
b Check for 28 VDC on pin 1 at VU side of 76CE.
c If there is 28 VDC repair wiring between pin 1 and H of 1842VT AWM 279297 for ENG 1 fault or pin H of 1833VT AWM 279296 for ENG 2 fault.
d If there is no 28 VDC, install relays 76CE and 79CE and continue to troubleshoot.
2 If there is no 28VDC at pin X, install relay 79CE continue to troubleshoot.
(4) If the fault continues:
(a) Examine the WF01 (4217KS) and WF02 (4218KS) harnesses, connectors P2 (4000KS-P2) and P1 (4000KS-P1) - EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) - Pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
1 Inspect for harness damage.
2 Inspect for loose or damaged 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 the fault continues or no problems are found with the harnesses, use a PLIERS - JAWED, SOFT to disconnect the electrical connectors P2 (4000KS-P2) and P1 (4000KS-P1) from the EEC (4000KS) and connectors P403 (403VC-A) and 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 connectors P2 (4000KS-P2) and P1 (4000KS-P1) to the EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(6) If the fault continues:
(a) Disconnect the electrical connectors P2 (4000KS-P2) and P1 (4000KS-P1) from the EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the TCM ground operation 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).
Table 2: TCM Discrete Channel B Connector Contacts
(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 the fault continues:
Check the aircraft wiring to the relays 79CE.
(a) For ENG 1 fault: remove relay 79CE1.
1 At pylon junction box, at (402VC1) and (403VC1) check for continuity between pins 1 and 2.
2 If a problem is found, repair aircraft wiring AWM 732546 and AWM 732548.
3 Install relay 79CE1.
4 Do the test given in Para. 3.
(b) For ENG 2 fault: remove relay 79CE2.
1 Put a shunt between pin 4 and 6 and between pin 2 and 8.
2 At pylon junction box, at (402VC2) and (403VC2) check for continuity between pins 1 and 2.
3 If a problem is found, repair aircraft wiring AWM 732547 and AWM 732549.
4 Remove shunts and install relay 79CE2.
5 Do the test given in Para. 3.
(8) If no problem is found on aircraft wiring or if the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
5. Close-up(1) Open the thrust reverser cowl-doors AMM 78-36-00-010-802.
(2) In 83VU for fault on ENG1 and 84VU for fault on ENG2, replace relays:
(a) If fault is on ENG 1, replace relays 76CE1 and 79CE1.
(b) If fault is on ENG 2, replace Relays 76CE2 and 79CE2.
(c) Do the test given in Para. 3.
(3) If the fault continues:
(a) Remove relays 79CE.
1 Check for 28 VDC at pin X on VU side of 79CE.
a If there is 28 VDC, remove relay 76CE.
b Check for 28 VDC on pin 1 at VU side of 76CE.
c If there is 28 VDC repair wiring between pin 1 and H of 1842VT AWM 279297 for ENG 1 fault or pin H of 1833VT AWM 279296 for ENG 2 fault.
d If there is no 28 VDC, install relays 76CE and 79CE and continue to troubleshoot.
2 If there is no 28VDC at pin X, install relay 79CE continue to troubleshoot.
(4) If the fault continues:
(a) Examine the WF01 (4217KS) and WF02 (4218KS) harnesses, connectors P2 (4000KS-P2) and P1 (4000KS-P1) - EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) - Pylon junction box, for problems which are possible between the EEC (4000KS) and the pylon junction box.
1 Inspect for harness damage.
2 Inspect for loose or damaged connectors.
NOTE: Loose connectors must be disconnected and examined for further wear or damage.
(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.
(5) If the fault continues or no problems are found with the harnesses, use a PLIERS - JAWED, SOFT to disconnect the electrical connectors P2 (4000KS-P2) and P1 (4000KS-P1) from the EEC (4000KS) and connectors P403 (403VC-A) and 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 connectors P2 (4000KS-P2) and P1 (4000KS-P1) to the EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(6) If the fault continues:
(a) Disconnect the electrical connectors P2 (4000KS-P2) and P1 (4000KS-P1) from the EEC (4000KS) and connectors P403 (403VC-A) and P402 (402VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the TCM ground operation 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: 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 |
Table 2: TCM Discrete Channel B Connector Contacts
| WF01 (4217KS) Harness P2(4000KS-P2) EEC (4000KS) Connector Contacts | WF01(4217KS) Harness P403 (403VC-A) Pylon Junction Box Connector Contacts |
|---|---|
| T | 1 |
| S | 2 |
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 the fault continues:
Check the aircraft wiring to the relays 79CE.
(a) For ENG 1 fault: remove relay 79CE1.
1 At pylon junction box, at (402VC1) and (403VC1) check for continuity between pins 1 and 2.
2 If a problem is found, repair aircraft wiring AWM 732546 and AWM 732548.
3 Install relay 79CE1.
4 Do the test given in Para. 3.
(b) For ENG 2 fault: remove relay 79CE2.
1 Put a shunt between pin 4 and 6 and between pin 2 and 8.
2 At pylon junction box, at (402VC2) and (403VC2) check for continuity between pins 1 and 2.
3 If a problem is found, repair aircraft wiring AWM 732547 and AWM 732549.
4 Remove shunts and install relay 79CE2.
5 Do the test given in Para. 3.
(8) If no problem is found on aircraft wiring or if the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
Subtask 73-00-00-860-217-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.
(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.