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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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03/04/21

Message Overview:

Message Name:

NO A-DCU-1 BUS OUTPUT

Message Code:

B3-006489

Associated CAS:

None

Reporting LRU: DCU 1
System Description: 31-41-00
Schematic Diagram: 31-41-00
Wiring Diagram: 31-41-01
31-41-02
31-41-03
31-41-13

Message Description:

No A-DCU-1 data received at L-IOC-1.

Possible Causes:

  • Data Concentrator Unit (DCU) (A14)
  • Left Input/Output Concentrator Unit (IOC) 1 (A4-IOC1)
  • Integrated Avionics Processing System (IAPS) (A4)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

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
Removal of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-000-801
Installation of the Integrated-Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-400-801
Removal of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-000-801
Installation of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-400-801
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 and L IAPS Circuit Breaker CB1-B6. Is the fault message still present?

    1. If NO, do close out.
    2. If YES, continue with next step.
      NOTE: Before you open the IAPS circuit breakers, make sure that all Engine FADEC circuit breakers are open. If the Engine FADEC circuit breakers remain closed, Engine Igniters will activate. This can cause injury to persons and damage to equipment.

  2. Swap left IOC with right IOC. Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, replace defective IOC.

  3. Do wiring check between DCU (A14) and the IAPS Card Cage (A4) for the following wires:

    From To Result
    Conn. A14FP1 - 2C Conn. A4P1 - 32
    Conn. A14FP1 - 2D Conn. A4P1 - 33

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

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

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

  5. Replace IAPS Card Cage (A4).
  6. Do close out.

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