Loss of Communication with the Data Link through the MCDU 1

TASK 22-82-00-810-819-A
Loss of Communication with the Data Link through the MCDU 1

1. Possible Causes

MCDU-1 [3CA1]
wiring of the ATSU-1 RECEIVER bus from the MCDU 1 (3CA1) to the first terminal block

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 22-82-12-000-001	Removal of the MCDU
AMM 22-82-12-400-002	Installation of the MCDU
ASM 228604
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

3. Fault Confirmation
Subtask 22-82-00-860-058-A

A. Job Set-up
(1) Aircraft Maintenance Configuration
(a) Energize the aircraft electrical circuits
AMM 24-41-00-861-002.
(b) Make sure that the ventilation of the electronics racks is in operation.

Subtask 22-82-00-710-086-C

B. Test

ACTION	RESULT
1.On the center pedestal, on the MCDU 1:	On the center pedestal, on the MCDU 1:
push the MCDU MENU mode key.	The MCDU MENU page comes into view.
push the line key adjacent to the ATSU indication.	The ATSU DATALINK page comes into view.

4. Fault Isolation
Subtask 22-82-00-810-076-C

A. If the ATSU DATALINK page does not come into view:

replace the MCDU-1 [3CA1] AMM 22-82-12-000-001 and AMM 22-82-12-400-002.

(1) If the fault continues:

do a check and repair the wiring of the ATSU-1 RECEIVER bus from the MCDU 1 (3CA1) to the first terminal block ASM 228604.

Subtask 22-82-00-710-087-A

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

5. Close-up
Subtask 22-82-00-860-059-A

A. Put the aircraft back to its initial configuration.
(1) De-energize the aircraft electrical circuits
AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:25:28 UTC