Failure of the Bus between the ECU 1 and the GCU 1

TASK 24-20-00-810-912-A
Failure of the Bus between the ECU 1 and the GCU 1

1. Possible Causes

GCU-1 [1XU1]
wiring

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 242201
AMM 24-22-34-000-001	Removal of the GCU-1(2)
AMM 24-22-34-400-001	Installation of the GCU-1(2)
AMM 24-41-00-740-002	Operational Check of the GAPCU via the CFDS
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 31-60-00-860-001	EIS Start Procedure
AMM 31-60-00-860-002	EIS Stop Procedure
AMM 71-00-00-710-003	Engine Automatic Start
AMM 71-00-00-710-028	Engine Shutdown
AMM 71-00-00-860-814	Shutdown of the Engine
AMM 71-00-00-860-823	Start the Engine (Normal Automatic Start)

3. Fault Confirmation
Subtask 24-20-00-869-107-A ** ON A/C NOT FOR ALL

A. Test
Not applicable.

4. Fault Isolation
Subtask 24-20-00-810-217-B ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the maintenance message ECU (E1-4000KS)/ GCU1 (1XU1) and by the upper ECAM-DU warning GEN 1 FAULT:

NOTE: You can find this message with other CFDS fault messages. First, do the trouble shooting for all the other CFDS fault messages.

replace the GCU-1 [1XU1] AMM 24-22-34-000-001 and AMM 24-22-34-400-001.

(1) If the fault continues:

do a check and repair the wiring ASM 242201 for an open circuit, a short to ground or a short to shield between:
. pin A/7E of the GCU 1 and pin J3/11 of the ECU (E1-4000KS)
. pin A/8E of the GCU 1 and pin J3/24 of the ECU (E1-4000KS)
. pin A/7E and pin A/9E of the GCU 1 (short to shield of the wiring)
. pin A/8E and pin A/9E of the GCU 1 (short to shield of the wiring).

Subtask 24-20-00-710-156-C ** ON A/C NOT FOR ALL

B. Do this operational test to make sure that the system operates correctly.
(1) Aircraft Maintenance Configuration
(a) Energize the aircraft electrical circuits
AMM 24-41-00-861-002.
(b) Do the EIS start procedure (Upper ECAM DU and lower ECAM DU only)
AMM 31-60-00-860-001.
(2) In the cockpit, on the ELEC panel 35VU:

Push, release and push again the GEN 1 pushbutton switch (3XU1).

(3) Do the BITE test of the GAPCU AMM 24-41-00-740-002.
(4) Start engine 1 AMM 71-00-00-860-823.
(5) Do this test:

ACTION	RESULT
On the ECAM control panel: Push the ELEC key to get the ELEC page.	On the lower ECAM DU: The correct electrical parameters of GEN 1 are shown and GEN 1 supplies the AC1 busbar.

Subtask 24-20-00-710-156-F ** ON A/C NOT FOR ALL

push, release and push again the GEN 1 pushbutton switch (3XU1).

(3) Do the operational test of the GAPCU AMM 24-41-00-740-002.
(4) Start the engine 1 AMM 71-00-00-710-003.
(5) Do this test:

ACTION	RESULT
On the ECAM control panel: get the ELEC page.	On the lower ECAM DU: the correct electrical parameters of the GEN 1 are shown and the AC1 busbar is supplied by the GEN 1.

5. Close-up
Subtask 24-20-00-860-190-C ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Stop engine 1 AMM 71-00-00-860-814.
(2) Do the EIS stop procedure
AMM 31-60-00-860-002.
(3) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
(4) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

Subtask 24-20-00-860-190-F ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Stop the engine 1 AMM 71-00-00-710-028.
(2) Do the EIS stop procedure
AMM 31-60-00-860-002.
(3) On the ECAM control panel, set the UPPER DISPLAY and LOWER DISPLAY potentiometers to OFF.
(4) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:26:23 UTC