Loss of Message Bus RS422 Between the FWC 2 and the DMC 2

TASK 31-63-00-810-960-A
Loss of Message Bus RS422 Between the FWC 2 and the DMC 2

1. Possible Causes

FWC-2 [1WW2]
DMC-2 [1WT2]
wiring from the FWC 2(1WW2) to the DMC 2(1WT2)

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 31-60-00-740-002	Perform Electronic Instrument System (EIS) Input Test
AMM 31-60-00-740-007	GROUND SCANNING Test of the DMC
AMM 31-63-34-000-001	Removal of the DMC
AMM 31-63-34-400-001	Installation of the DMC

3. Fault Confirmation
Subtask 31-63-00-865-189-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	EIS/FWC2/SPLY	2WW	Q07

Subtask 31-63-00-740-330-A ** ON A/C NOT FOR ALL

B. Test
Do the EIS input test (system 1) AMM 31-60-00-740-002.

Subtask 31-63-00-740-330-B ** ON A/C NOT FOR ALL

B. Test
Do the Ground Scanning Test of the DMC AMM 31-60-00-740-007.

4. Fault Isolation
Subtask 31-63-00-810-208-A ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message DMC2: NO FWC2 MSG:

replace the FWC-2 [1WW2] AMM 31-53-34-000-001 and AMM 31-53-34-400-001.

(1) If the fault continues:

replace the DMC-2 [1WT2] AMM 31-63-34-000-001 and AMM 31-63-34-400-001.

(a) If the fault continues:

do a check and repair the wiring from the FWC 2(1WW2) to the DMC 2(1WT2), pins AE/14B, 14C to pins AA/9H, 9G ASM 315205.

Subtask 31-63-00-810-208-B ** ON A/C NOT FOR ALL

A. If the test gives the maintenance message FWC2(1WW2) BUS MESSAGEX/DMC2(1WT2)

replace the FWC-2 [1WW2] AMM 31-53-34-000-001 and AMM 31-53-34-400-001.

(1) If the fault continues:

replace the DMC-2 [1WT2] AMM 31-63-34-000-001 and AMM 31-63-34-400-001.

(a) If the fault continues:

do a check and repair the wiring from the FWC 2(1WW2) to the DMC 2(1WT2), pins AE/14B, 14C to pins AD/5C, 5D ASM 315205.

Subtask 31-63-00-740-331-A

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

[Rev.8 from Aug 2018] 2026.04.04 04:30:49 UTC