BMC-1 Bus Fault on EIU-1

TASK 73-25-00-810-B37-A
BMC-1 Bus Fault on EIU-1

1. Possible Causes

BMC-1 [1HA1]
wiring
EIU-1 [1KS1]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AWM 361111
AMM 36-11-34-000-001	Removal of the BMC
AMM 36-11-34-400-001	Installation of the BMC
AMM 73-25-34-000-802	Removal of the Engine Interface Unit (EIU)
AMM 73-25-34-400-802	Installation of the Engine Interface Unit (EIU)
AMM 73-25-34-710-802	Operational Test of the Engine Interface Unit (EIU) with the Centralized Fault Display System (CFDS)
AWM 732557

3. Fault Confirmation
Subtask 73-25-00-710-576-A ** ON A/C NOT FOR ALL

A. Do the operational test of the Engine Interface Unit (EIU-1) (1KS1) with the Centralized Fault Display System (CFDS) to confirm this fault. Refer to AMM 73-25-34-710-802.

4. Fault Isolation
Subtask 73-25-00-810-460-A ** ON A/C NOT FOR ALL

A. Do as follows:
(1) Do the operational test of the Engine Interface Unit (EIU-2) (1KS2) with the Centralized Fault Display System (CFDS) to confirm this fault AMM 73-25-34-710-802.
(2) If the fault is confirmed on EIU-1 and EIU-2:
(a) Replace BMC-1 [1HA1] AMM 36-11-34-000-001 and AMM 36-11-34-400-001.
1 Do the test given in Para. 3.
(b) If the fault continues:
1 Remove the BMC-1 (1HA1) AMM 36-11-34-000-001.
2 Test the circuits AWM 732557 and AWM 361111. Refer to table 1. Look for:
a Wire-to-wire shorts
b Shorts-to-ground
c Continuity (less than 5 ohms resistance).

NOTE: A short-to-ground is found when the resistance is less than 100 000 (100K) ohms.

Table 1: BMC-1 Circuit Connector Contacts

BMC-1 (1HA1) Connector AA Contacts	1862VT (86VU) Contacts
13B	S
15B	G

(3) If you find damage:
(a) Repair or replace wiring AWM 732557.
(b) Install the BMC-1 (1HA1) AMM 36-11-34-400-001.
(c) Do the test given in Para. 3.
(4) If you find no damage or if the fault continues:
(a) Remove the EIU-1 (1KS1) AMM 73-25-34-000-802.
(b) Test the circuits AWM 732557. Refer to table 2. Look for:
1 Wire-to-wire shorts
2 Shorts-to-ground
3 Continuity (less than 5 ohms resistance).

NOTE: A short to ground is found when the resistance is less than 100,000 (100K) ohms.

Table 2: EIU-1 Circuit Connector Contacts

EIU-1 (1KS1) Connector AA Contacts	1862VT (86VU) Contacts
14C	T
15C	P

(5) If you find damage:
(a) Repair or replace wiring AWM 732557.
(6) If you find no damage or if the fault continues:
(a) Replace EIU-1 [1KS1] AMM 73-25-34-400-802.
(b) Do the test given in Para. 3.

5. Close-up
Subtask 73-25-00-860-182-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.

[Rev.8 from Aug 2018] 2026.04.04 04:36:51 UTC