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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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Quick Links

03/04/21

Message Overview:

Message Name:

NO A-DCU-8 BUS OUTPUT

Message Code:

B3-006494

Associated CAS:

None

Reporting LRU: DCU 1
System Description: 31-41-00
Schematic Diagram: 31-41-00
Wiring Diagram: 23-51-12
31-41-01
31-41-02

Message Description:

A-DCU-8 bus data absent at L-RIU.

Possible Causes:

  • Data Concentrator Unit (DCU) (A14)
  • Left Radio Interface Unit (RIU 1) (A17)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Radio Interface Unit (RIU) AMM 23-51-21-000-801
Installation of the Radio Interface Unit (RIU) AMM 23-51-21-400-801
Removal of the Data Concentrator Unit (DCU) AMM 31-41-01-000-802
Installation of the Data Concentrator Unit (DCU) AMM 31-41-01-400-802
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset EICAS DCU A Circuit Breaker CB1-D1, RIU 1A Circuit Breaker CB1-B5 and RIU/AURAL 1B Circuit Breaker CB1-B4. Is the fault message still present?

    1. If NO, do close out.
    2. If YES, continue with next step.

  2. Do wiring check between DCU (A14), and RIU 1 (A17) for the following wires:

    From To Result
    Conn A14FP1 - 9A Conn A17P1 - 63
    Conn A14FP1 - 9B Conn A17P1 - 64

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair wiring.

  3. Replace DCU (A14). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

  4. Replace RIU 1 (A17).
  5. Do close out.

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