Fault Message:

EMS CDU 1/DCPC LEFT FTM-A12/WRG

Fault Code:

2470104CDU

Associated CAS:

ELEC SYS FAULT
(Advisory)

ARINC 429 communication between the DC Power Center (DCPC) and the Electrical Management System Control and Display Units (EMS CDU) is faulty. The LRU transmits on periodic basis a test label that is turned around by the receiving LRU.

• Electrical Management System Control and Display Unit (EMS CDU) 1 (A94)
• DC Power Center (DCPC) (A63)
• DC Power Center (DCPC) Microprocessor Card
• DC Power Center (DCPC) Supervisor Card
• Secondary Power Distribution Assembly (SPDA) 1 (A13)
• Secondary Power Distribution Assembly (SPDA) 4 (A16)
• DC Power Center (DCPC) Secondary Power Distribution Assembly (SPDA) Feeder Card 1
• DC Power Center (DCPC) Secondary Power Distribution Assembly (SPDA) Feeder Card 2
• DC Power Center (DCPC) Secondary Power Distribution Assembly (SPDA) Feeder Card 3
• DC Power Center (DCPC) Secondary Power Distribution Assembly (SPDA) Feeder Card 4
• Primary Logic Card (PLC) 1
• Primary Logic Card (PLC) 2
• Primary Logic Card (PLC) 3
• DC Power Quality Monitor Card (DCPQM) 1
• DC Power Quality Monitor Card (DCPQM) 2
• Cabin DC Feeder Card
• Battery/Ram-Air-Turbine (BATT/RAT) Card
• Junction Box (JB3)/PCB3
• Junction Box (JB3)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Make sure the Junction Box 3 is racked properly. Field experience revealed many cases of Junctions Boxes not installed properly.
2. Flight deck effect:

   1. DC synoptic page all magenta.
   2. On the EMS CDU, DCPC electrical loads are dashed.

3. Alternative fault confirmation:

   1. On EMS CDU 1, select Diagnostic mode.

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

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

      1. DCPC IN=0=loss of communication from DCPC left microprocessor to EMS CDU 1
      2. PCDA OUT=0=loss of communication from EMS CDU 1 to DCPC, DCPC, SPDA 1, SPDA 2, SPDA 3, SPDA 4, EMS CDU 2.
         

1. Swap EMS CDU 1 with EMS CDU 2.

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

2. Swap DCPC microprocessor cards.

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

3. Replace DCPC supervisor card.

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

   - For EMI Filter/Wiring check

4. Remove both microprocessor cards.
5. Perform wiring checks between EMS CDU, JB3, SPDA 1, SPDA 2 and DCPC.

   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.

6. Perform wiring checks between DCPC connectors and microprocessors.

   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.
      CAUTION: To prevent damage to the DCPC motherboard connectors, ensure that the wire jumper pin outside diameter (OD)/socket inside diameter (ID) does not exceed 0.025 inch.

7. Replace EMS CDU.

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

8. Swap SPDA 1 with SPDA 2.

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

9. Swap SPDA 4 with SPDA 3.

   1. If system checks good, replace SPDA 4 and do close out.
   2. If fault remains, continue with next step.

10. Swap DCPC.

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

11. Replace JB3.

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

    - For DCPC Data Bus check

12. Make sure that the EXT AC cord is not connected to the aircraft.
13. Remove one of four DCPC SPDA Feeder cards one at a time and set Battery Master Switch to ON to determine faulty SPDA Feeder card.
    NOTE: Monitor the fault via the AC Synoptic page or the Counters (EMS CDU Diagnostic Mode).
14. Replace defective DCPC SPDA Feeder card.

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

15. Remove one of three PLC cards one at a time and set Battery Master Switch to ON to determine faulty PLC.
16. Replace defective PLC.

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

17. Remove one of two DCPQM cards one at a time and set Battery Master Switch to ON to determine faulty DCPQM.
18. Replace defective DCPQM cards.

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

19. Replace Cabin DC Feeder card.

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

20. Check to see if the fault has gone away.

    1. If YES, replace the defective Cabin DC Feeder card and do close out.
    2. If NO, continue with next step.

21. Replace BATT/RAT card.

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

22. Replace DCPC.
23. Do close out.
    Detailed Troubleshooting with pin assignment