DOC AIRBUS | TSM A320FLoss of 28VDC Power Supply of the ECU on the Engine 1
TASK 73-25-00-810-948-A
Loss of 28VDC Power Supply of the ECU on the Engine 1
1. Possible Causes
A. Referenced Information
3. Fault Confirmation
Subtask 73-25-00-710-343-A ** ON A/C NOT FOR ALL
Subtask 73-25-00-810-200-A ** ON A/C NOT FOR ALL
[Rev.8 from Aug 2018]
2026.04.04 04:35:51 UTC
Loss of 28VDC Power Supply of the ECU on the Engine 1
1. Possible Causes
- EIU-1 [1KS1]
- ECU [4000KS]
- aircraft wiring
- C/B-ENGINE/1/FADEC A/AND EIU 1 [2KS1]
- C/B-ENGINE/ENG1/FADEC B/AND EIU 1 [4KS1]
- harnesses J1 and J2
A. Referenced Information
| REFERENCE | DESIGNATION |
|---|---|
| AMM 73-21-60-000-001 | Removal of the Electronic Control Unit (ECU) |
| AMM 73-21-60-400-001 | Installation of the Electronic Control Unit (ECU) |
| ASM 732505 | |
| ASM 732508 | |
| AMM 73-25-34-000-040 | Removal of the Engine Interface Unit (EIU) |
| AMM 73-25-34-400-040 | Installation of the Engine Interface Unit (EIU) |
| AMM 73-29-00-710-040 | Operational Test of the FADEC on the ground (with Engine Motoring) |
Subtask 73-25-00-710-343-A ** ON A/C NOT FOR ALL
A. Do the operational test of the FADEC 1B on the ground (with engine motoring) AMM 73-29-00-710-040.
4. Fault IsolationSubtask 73-25-00-810-200-A ** ON A/C NOT FOR ALL
A. If the test gives the maintenance message EIU, ECU (CR3 DIODE):
Subtask 73-25-00-710-344-A ** ON A/C NOT FOR ALL - disconnect the connectors J1 and J2 from the ECU (4000KS) and do a check for 28VDC at pins J1/13 and J2/13 with the FADEC GND PWR pushbutton switch released (the ON legend is on) ASM 732505.
- replace the EIU-1 [1KS1] (the most possible failure is the EIU 28V relay) AMM 73-25-34-000-040 and AMM 73-25-34-400-040
- replace the ECU [4000KS] (the most possible failure is an ECU diode) AMM 73-21-60-000-001 and AMM 73-21-60-400-001.
- do a check for 28VDC at EIU 1 (1KS1) pins AC/9, 11 ASM 732505.
- do a check for open or short to ground at the aircraft wiring from the circuit breakers (2KS1) and (4KS1) to EIU 1 (1KS1) pins AC/9, 11.
- repair the above wiring.
- replace the defective C/B-ENGINE/1/FADEC A/AND EIU 1 [2KS1] or C/B-ENGINE/ENG1/FADEC B/AND EIU 1 [4KS1] .
- do a check for open or short to ground at the harnesses J1 and J2 between the EIU 1 (1KS1) and the ECU (4000KS), pins AC/2, 7 to pins J1/13, J2/13. Replace the harness J1 or J2 if necessary ASM 732505.
- make sure that there is no ground signal at EIU 1 (1KS1) pin AA/5B ASM 732508.
- replace the EIU-1 [1KS1] AMM 73-25-34-000-040 and AMM 73-25-34-400-040.
B. Do the test given in Para. 3.A.