Loss of the MESSAGE 3 Bus from the FWC 1 and the FWC 2 to the DMC 3

TASK 31-53-00-810-960-A
Loss of the MESSAGE 3 Bus from the FWC 1 and the FWC 2 to the DMC 3

1. Possible Causes

FWC-1 [1WW1]
FWC-2 [1WW2]
DMC-3 [1WT3]
wiring for the MESSAGE 3 bus from the FWC 1 pins AB/14J,14K to the DMC 3 pins AA/9C,9H and from the FWC 2 pins AB/14J,14K to the DMC 3 pins AA/9G,9H
wiring for the MESSAGE 3 bus from the FWC 1 pins AB/14J,14K to the DMC 3 pins AD/5G,5H and from the FWC 2 pins AB/14J,14K to the DMC 3 pins AD/5C,5D

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 315205
AMM 31-53-34-000-001	Removal of the Flight Warning Computer (FWC)
AMM 31-53-34-400-001	Installation of the Flight Warning Computer (FWC)
AMM 31-60-00-740-004	EIS System Test
AMM 31-63-34-000-001	Removal of the DMC
AMM 31-63-34-400-001	Installation of the DMC

3. Fault Confirmation
Subtask 31-53-00-740-084-A

A. Test
Do the EIS System Test AMM 31-60-00-740-004.

4. Fault Isolation
Subtask 31-53-00-810-214-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance messages NO FWC1 MSG and NO FWC2 MSG:

(1) If the fault continues:

(2) If the fault continues:

remove the FWC-1 [1WW1]
remove the DMC-3 [1WT3]
remove the FWC-2 [1WW2]
do a check and repair the wiring for the MESSAGE 3 bus from the FWC 1 pins AB/14J,14K to the DMC 3 pins AA/9C,9H and from the FWC 2 pins AB/14J,14K to the DMC 3 pins AA/9G,9H ASM 315205.
Install the FWC-2 [1WW2]
Install the DMC-3 [1WT3]
Install the FWC-1 [1WW1]

Subtask 31-53-00-810-214-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance messages FWC1(1WW1)BUS MESSAGE3/DMC3(1WT3) and FWC2(1WW2)BUS MESSAGE3/DMC3(1WT3):

(1) If the fault continues:

(2) If the fault continues:

remove the FWC-1 [1WW1]
remove the DMC-3 [1WT3]
remove the FWC-2 [1WW2]
do a check and repair the wiring for the MESSAGE 3 bus from the FWC 1 pins AB/14J,14K to the DMC 3 pins AD/5G,5H and from the FWC 2 pins AB/14J,14K to the DMC 3 pins AD/5C,5D ASM 315205.
Install the FWC-2 [1WW2]
Install the DMC-3 [1WT3]
Install the FWC-1 [1WW1]

Subtask 31-53-00-740-094-A

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

[Rev.8 from Aug 2018] 2026.04.04 04:30:21 UTC