DOC AIRBUS | TSM A320FChannel to Channel TCM Discrete Disagreement
TASK 73-21-00-810-899-A
Channel to Channel TCM Discrete Disagreement
1. Possible Causes
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Fault Confirmation
Subtask 73-21-00-710-152-A ** ON A/C NOT FOR ALL
Subtask 73-21-00-860-091-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:36:42 UTC
Channel to Channel TCM Discrete Disagreement
1. Possible Causes
- HARNESS-FAN, WF02 [4218KS]
- HARNESS-FAN, WF01 [4217KS]
GND/DLE mechanical relay (79CE1) GND/DLE mechanical relay (79CE2) - wiring
[4000KS]
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 70-70-00-910-803 | SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses |
| AMM 73-21-00-710-807 | Test No.6 - EEC Operation Test (Idle 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 73-21-00-710-152-A ** ON A/C NOT FOR ALL
A. Do a FADEC system idle test to confirm this fault AMM 73-21-00-710-807.
(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) in channel A and channel B, go to the Para. Fault Isolation.
4. Fault IsolationNOTE: The Electronic Engine Control (EEC) has detected that the Throttle Control Malfunction (TCM) discrete circuits do not agree between channel A and channel B.
(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) in channel A and channel B, 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 73-21-00-810-171-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) Examine the WF02 (4218KS) and WF01 (4217KS) harnesses, connectors P1 (4000KS-P1) and P2 (4000KS-P2) - EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-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, or
2 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
3 Do the test given in Para. 3.
(3) 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) and connectors P402 (402VC-A) and P403 (403VC-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 P1 (4000KS-P1) and P2 (4000KS-P2) to the EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connectors P1 (4000KS-P1) and P2 (4000KS-P2) from the EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the TCM discrete 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, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802, or
2 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
3 Do the test given in Para. 3.
(5) If no problems are found with the harnesses or the fault continues, check aircraft relay and wiring.
(a) In the avionics compartment, on the shelf 83VU:
1 For ENG 1 fault: replace theGND/DLE mechanical relay (79CE1) .
2 For ENG 2 fault: replace theGND/DLE mechanical relay (79CE2) .
3 Do the test given in Para. 3.
(b) If the fault continues, check aircraft wiring:
2 Do a check for continuity between pins B and C and between pins A and D.
3 Do a check for short to ground and wire-to-wire short at pins 4 and 6 and pins 2 and 8.
4 Put a shunt between pins 4 and 6 and between pins 2 and 8.
5 At pylon junction box, disconnect (402VC-A).
6 At connector (402VC), do a check for continuity between pins 1 and 2.
7 At pylon junction box, disconnect (403VC-A).
8 At connector (403VC), do a check for continuity between pins 1 and 2.
9 Repair or replace the aircraft wiring as necessary:
a For ENG 1 fault, refer to AWM 732546 and AWM 732548.
b For ENG 2 fault, refer to AWM 732547 and AWM 732549.
10 Remove the shunts, install GND/DLE mechanical relay 79CE1(2) and connect (402VC-A) and (403VC-A).
11 Do the test given in Para. 3.
(6) If no problems are found with the aircraft relay or wirings 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) Examine the WF02 (4218KS) and WF01 (4217KS) harnesses, connectors P1 (4000KS-P1) and P2 (4000KS-P2) - EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-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 harnesses or connectors: 1 Replace HARNESS-FAN, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802, or
2 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
3 Do the test given in Para. 3.
(3) 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) and connectors P402 (402VC-A) and P403 (403VC-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 P1 (4000KS-P1) and P2 (4000KS-P2) to the EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-A) to the pylon junction box.
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Disconnect the electrical connectors P1 (4000KS-P1) and P2 (4000KS-P2) from the EEC (4000KS) and connectors P402 (402VC-A) and P403 (403VC-A) from the pylon junction box. Use a MULTIMETER - STANDARD to test the TCM discrete 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, WF02 [4218KS] AMM 73-21-62-000-802 and AMM 73-21-62-400-802, or
2 Replace HARNESS-FAN, WF01 [4217KS] AMM 73-21-61-000-802 and AMM 73-21-61-400-802.
3 Do the test given in Para. 3.
(5) If no problems are found with the harnesses or the fault continues, check aircraft relay and wiring.
(a) In the avionics compartment, on the shelf 83VU:
1 For ENG 1 fault: replace the
2 For ENG 2 fault: replace the
3 Do the test given in Para. 3.
(b) If the fault continues, check aircraft wiring:
- For ENG 1 fault: AWM 732546 and AWM 732548
- For ENG 2 fault: AWM 732547 and AWM 732549.
2 Do a check for continuity between pins B and C and between pins A and D.
3 Do a check for short to ground and wire-to-wire short at pins 4 and 6 and pins 2 and 8.
4 Put a shunt between pins 4 and 6 and between pins 2 and 8.
5 At pylon junction box, disconnect (402VC-A).
6 At connector (402VC), do a check for continuity between pins 1 and 2.
7 At pylon junction box, disconnect (403VC-A).
8 At connector (403VC), do a check for continuity between pins 1 and 2.
9 Repair or replace the aircraft wiring as necessary:
a For ENG 1 fault, refer to AWM 732546 and AWM 732548.
b For ENG 2 fault, refer to AWM 732547 and AWM 732549.
10 Remove the shunts, install GND/DLE mechanical relay 79CE1(2) and connect (402VC-A) and (403VC-A).
11 Do the test given in Para. 3.
(6) If no problems are found with the aircraft relay or wirings or if the fault continues:
(a) Replace
(b) Do the test given in Para. 3.
Subtask 73-21-00-860-091-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.