Fault Message:

CDU 2/SPDA 1 / WRG

Fault Code:

2462602SPD

Associated CAS:

ELEC SYS FAULT
(Advisory)

ARINC 429 communication between the Secondary-Power Distribution Assembly (SPDA) 1 and the Electrical Management System Control-and-Display Unit (EMS CDU) 2 is faulty. The Line Replacement Unit (LRU) transmits a test label on a periodic basis and the label is echoed back by the receiving LRU.

• Electrical Management System Control-and-Display Unit (EMS CDU) 2 (A91)
• Secondary-Power Distribution Assembly (SPDA) 1 (A13)
• Junction Box (JB4)
• PCB2/Junction Box (JB4)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Make sure the JB4 is racked properly.Field experience revealed many cases of Junction Boxes not installed properly.
Fault confirmation:

1. Flight deck effect:

• On the EMS CDU 1, SPDA 1 electrical loads are dashed

2. Alternative fault confirmation:

   • On EMS CDU 1, select Diagnostic mode

     • Select SYSTEM - CNTL key (page 1/3)
     • Select lower left side key
     • Select lower right side key

   • On EMS CDU 1, select CIRCUIT BREAKER - SYS key and COUNTERS

     • SPDA 1 IN=0=loss of communication from SPDA 1 to EMS CDU 1
     • PCDA OUT=0=loss of communication from EMS CDU 1 to ACPC, DCPC, SPDA 1, SPDA 2, SPDA 3, SPDA 4, and EMS CDU 2

1. Swap EMS CDU 2 with EMS CDU 1.

   1. If system checks are good, replace EMS CDU 2 and do close out.
   2. If fault remains, continue with next step.

2. Swap the SPDA 1 with SPDA 3.

   1. If system checks are good, replace SPDA 1 and do close out.
   2. If fault remains, continue with next step.

3. Perform wiring checks between EMS CDU 2 and SPDA 1, SPDA 4, SPDA 2, DCPC, ACPC and SPDA 3.

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

4. Replace JB4 PCB2/JB4.
5. Do close out.