(2)  
The maintenance message is identical for the left and right air data inertial reference systems (ADIRS). The left ADIRS maintenance message is shown on the ADIRS L BITE page on the control display unit (CDU). The right ADIRS maintenance message is shown on the ADIRS R BITE page on the CDU.

(3)  
Selected display options and configurations are set by ADR program pins. The status of these program pins are monitored by the ADIRU during power up.

(4)  
This message shows when the ADIRU detects an invalid program pin configuration of the air data reference.

(5)  
This fault causes the status code 21 to show on the inertial system display unit (ISDU) and the FAULT light on the mode select unit (MSU) to come on.

(6)  
This is a critical fault which also causes the status code 02 to show on the ISDU.

B.  Possible Causes
(1)
ADIRU, M1749 (left) or M1752 (right).

(2)
Wiring problem

EFFECTIVITY

34-21 TASKS 811-812
SIL ALL
Page 221 D633A103-SIL Oct 15/2008

C.  Circuit Breakers
(1)  These are the primary circuit breakers related to the fault:
CAPT Electrical System Panel, P18-1
Row Col Number Name
E 5 C01009 ADIRU LEFT DC
E 7 C01007 ADIRU LEFT AC

CAPT Electrical System Panel, P18-2
Row Col Number Name
E 8 C00425 ADIRU LEFT EXC

F/O Electrical System Panel, P6-1
Row Col Number Name
C 14 C01008 ADIRU RIGHT AC
C 15 C00426 ADIRU RIGHT EXC
C 17 C01010 ADIRU RIGHT DC

D.  Related Data
(1)
(WDM 34-21)

(2)
(SSM 34-21)

E.  Initial Evaluation
(1)  
For
the
applicable
ADIRS,
do
this
task:
ADIRS
BITE
Procedure,
34-21
TASK
801.

(2)  
If the maintenance message does not show on the CDU and the status code does not show on the ISDU, then there was an intermittent fault.

(3)  
If the maintenance message shows on the CDU and the status code shows on the ISDU, then do the Fault Isolation Procedure below.

F.  Fault Isolation Procedure
(1) Replace the applicable ADIRU.
These are the tasks:
Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801,
Air Data Inertial Reference Unit Installation, AMM TASK 34-21-01-400-801.

(a)
Do a check of the condition of the pins and connectors of the applicable ADIRU.

(b)
For
the
applicable
ADIRS,
do
this
task:
ADIRS
BITE
Procedure,
34-21
TASK
801.

1)  If the maintenance message does not show on the CDU, and the status code does not show on the ISDU, then you corrected the fault.
2)  If the maintenance message does show on the CDU, and the status code does show on the ISDU, then continue.
(2)  Do this check of the wiring of the program pins for the applicable ADIRU:
(a)  
Remove the ADIRU. To remove it, do this task: Air Data Inertial Reference Unit Removal, AMM TASK 34-21-01-000-801.

(b)  
Do a wiring check of the following program pins for a ground or an open circuit, per WDM 34-21-11, WDM 34-21-12, WDM 34-21-13, WDM 34-21-21, WDM 34-21-22, WDM 34-21-23, WDM 34-21-24, WDM 34-21-14.

EFFECTIVITY SIL ALL  34-21 TASK 812 
D633A103-SIL BOEING PROPRIETARY -Copyright # Unpublished Work -See title page for details  Page 222 Oct 15/2008 

NOTE: Open circuit pins are not shown on the WDMs.
(c)  For the left ADIRU, do the check of these pins at connector D3687B. For the right ADIRU, do the check of these pins at connector D3693B:
　
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