DMU Receives No Data from MCDU 1 or MCDU 2

TASK 31-36-00-810-865-A
DMU Receives No Data from MCDU 1 or MCDU 2

1. Possible Causes

wiring
MCDU-1 [3CA1]
MCDU-2 [3CA2]
DMU [1TV]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 22-70-00-710-001	Operational Test of the Multipurpose Control and Display Unit (MCDU)
AMM 31-36-00-710-001	Test of the DMU
AMM 31-36-34-000-001	Removal of the Data Management Unit (DMU)
AMM 31-36-34-400-001	Installation of the Data Management Unit (DMU)
ASM 313701

3. Fault Confirmation
Subtask 31-36-00-740-150-A ** ON A/C NOT FOR ALL

A. Do the DMU (1TV) fault monitoring test AMM 31-36-00-710-001.

NOTE: Make sure that the circuit breakers 1TV, 11CA1, 11CA2 on the panel 121VU and 11CA1 on the panel 49VU are closed during the test.

4. Fault Isolation
Subtask 31-36-00-810-102-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message:

MCDU 1 COMMUNIC FAIL, or
MCDU 2 COMMUNIC FAIL

(1) Do the operational test of the Flight Management System AMM 22-70-00-710-001.

(a) If the test gives a different maintenance message, you can find the related trouble shooting procedure in the applicable Page Block 201.

(2) If the fault continues:

do a check and repair the wiring from the MCDU-1 [3CA1] or MCDU-2 [3CA2] to the DMU [1TV] ASM 313701:

MCDU 1 Connector A/27 to DMU Connector AA/11A
MCDU 1 Connector A/28 to DMU Connector AA/11B
MCDU 1 Connector A/11 to DMU Connector AA/11E
MCDU 1 Connector A/12 to DMU Connector AA/11F
or
MCDU 2 Connector A/27 to DMU Connector AB/11A
MCDU 2 Connector A/28 to DMU Connector AB/11B
MCDU 2 Connector A/11 to DMU Connector AA/11E
MCDU 2 Connector A/12 to DMU Connector AA/11F

(3) If the fault continues:

replace the DMU (1TV) AMM 31-36-34-000-001 and AMM 31-36-34-400-001.

Subtask 31-36-00-740-151-A ** ON A/C NOT FOR ALL

B. Do the test given in Para. 3.

[Rev.8 from Aug 2018] 2026.04.04 04:40:06 UTC