Loss of the ILS 1 OR MMR 1 Bus Input on the ISIS Indicator

TASK 34-22-00-810-808-A
Loss of the ILS 1 OR MMR 1 Bus Input on the ISIS Indicator

1. Possible Causes

wiring of the ILS 1 OR MMR 1 (PORT 2) bus from the ISIS indicator (22FN) to the MMR-1 (40RT1)
IND-ISIS [22FN]
MMR-1 [40RT1]
wiring of the ILS 1 OR MMR 1 (PORT 2) bus from the ISIS indicator (22FN) to the ILS-1 (2RT1)
C/B-NAV/ILS/1 [1RT1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
ASM 342202
AMM 34-22-25-000-001	Removal of the ISIS Indicator
AMM 34-22-25-400-001	Installation of the ISIS Indicator
AMM 34-36-00-740-002	BITE Test of the ILS
AMM 34-36-00-740-003	BITE Test of the MMR
AMM 34-36-31-000-001	Removal of the ILS Receiver
AMM 34-36-31-400-001	Installation of the ILS Receiver

3. Fault Confirmation
Subtask 34-22-00-700-054-A ** ON A/C NOT FOR ALL

A. Test
Not applicable, you cannot confirm this fault on the ground.

4. Fault Isolation
Subtask 34-22-00-810-059-A ** ON A/C NOT FOR ALL

A. If the fault symptom is identified by the maintenance message on the face of the ISIS indicator:
ILS1(2RT1-1RT1) OR MMR1(40RT1)/ISIS(22FN-10FC)
and by the red flags on the face of the ISIS indicator:
LOC
or
G/S

do the BITE test of the MMR (system 1) AMM 34-36-00-740-003.

(1) If the test gives a maintenance message, do the trouble shooting procedure related to the maintenance message.
(2) If the test is OK:

do a check of the wiring of the ILS 1 OR MMR 1 (PORT 2) bus from the ISIS indicator (22FN) to the MMR-1 (40RT1) ASM 342202.

(a) If there is no continuity:

replace the defective wiring.

(b) If there is continuity:

replace the IND-ISIS [22FN] AMM 34-22-25-000-001 AMM 34-22-25-400-001.

1 After the subsequent flight, if the fault continues:

replace the MMR-1 [40RT1] AMM 34-36-31-000-001 AMM 34-36-31-400-001.

Subtask 34-22-00-810-059-C ** ON A/C NOT FOR ALL

do the BITE test of the ILS (system 1) AMM 34-36-00-740-002.

(1) If the test gives a maintenance message, do the trouble shooting procedure related to the maintenance message.
(2) If the test is OK:

do a check of the wiring of the ILS 1 OR MMR 1 (PORT 2) bus from the ISIS indicator (22FN) to the ILS-1 (2RT1) ASM 342202.

(a) If there is no continuity:

replace the defective wiring.

(b) If there is continuity:

replace the [22FN] AMM 34-22-25-000-001 AMM 34-22-25-400-001.

1 After the subsequent flight, if the fault continues:

replace the C/B-NAV/ILS/1 [1RT1] AMM 34-36-31-000-001 AMM 34-36-31-400-001.

[Rev.8 from Aug 2018] 2026.04.04 04:32:55 UTC