Loss of the 28VDC Power Supply of the ECU on the Engine 2

TASK 73-25-00-810-947-A
Loss of the 28VDC Power Supply of the ECU on the Engine 2

1. Possible Causes

EIU-2 [1KS2]
ECU [4000KS]
aircraft wiring
C/B-ENGINE/ENG2/FADEC B/AND EIU 2 [4KS2]
harness J2

2. Job Set-up Information
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)

3. Fault Confirmation
Subtask 73-25-00-865-055-A ** ON A/C NOT FOR ALL

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
121VU	ENGINE/ENG2/FADEC B/AND EIU 2	4KS2	Q40

Subtask 73-25-00-710-341-A ** ON A/C NOT FOR ALL

B. Test
(1) Do the operational test of the FADEC 2B on the ground (with engine motoring) AMM 73-29-00-710-040.
(2) If the circuit breaker (4KS2) is open, refer to Para. 4.A.(2).

4. Fault Isolation
Subtask 73-25-00-810-199-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message EIU - 28V, ECU:

do a check of the status of the circuit breaker (4KS2).

(1) If the circuit breaker is closed:

disconnect the connector J2 from the ECU (4000KS) and do a check for 28VDC at pin J2/13 with the FADEC GND PWR pushbutton switch released (the ON legend is on) ASM 732505.

(a) If there is 28VDC:

replace the EIU-2 [1KS2] (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.

(b) If there is no 28VDC:

do a check for 28VDC at EIU 2 (1KS2) pin AC/9 ASM 732505.

1 If there is no 28VDC:

do a check for open or short to ground at the aircraft wiring from the circuit breaker (4KS2) to EIU 2 (1KS2) pins AC/9.

a If there is a short to ground:

repair the above wiring.

b If there is no short to ground:

replace the C/B-ENGINE/ENG2/FADEC B/AND EIU 2 [4KS2] .

2 If there is 28VDC:

do a check for open or short to ground at the harness J2 between the EIU 2 (1KS2) and the ECU (4000KS), pin AC/2 to pin J2/13. Replace the harness J2 if necessary ASM 732505.

3 If the fault continues:

make sure that there is no ground signal at EIU 2 (1KS2) pin AA/5B ASM 732508.

replace the EIU-2 [1KS2] AMM 73-25-34-000-040 and AMM 73-25-34-400-040.

(2) If the circuit breaker (4KS2) is open:

close the circuit breaker.

(a) If the circuit breaker trips:

replace the EIU-2 [1KS2] AMM 73-25-34-000-040 and AMM 73-25-34-400-040
replace the ECU [4000KS] AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

(b) If the fault continues:

do a check for a short to ground at the harness J2 between the EIU 2 (1KS2) and the ECU (4000KS), pin AC/2 to pin J2/13.

1 If there is a short to ground:

replace the harness J2 .

2 If there is no short to ground:

do a check for a short to ground at the aircraft wiring between EIU 2 (1KS2) pin AC/9 and the circuit breaker (4KS2).

a If there is a short to ground:

repair the above wiring.

b If there is no short to ground:

replace the C/B-ENGINE/ENG2/FADEC B/AND EIU 2 [4KS2] .

Subtask 73-25-00-710-342-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:35:51 UTC