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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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03/08/21

Message Overview:

Message Name:

NO B-DCU-4 BUS OUTPUT

Message Code:

B3-006528

Associated CAS:

None

Reporting LRU: DCU 2
System Description: 31-41-00
Schematic Diagram: 31-41-00
Wiring Diagram: 31-41-01
31-41-02
31-41-11
31-41-13

Message Description:

NO B-DCU-4 data received at IASC1-B and IASC2-B.

Possible Causes:

  • Data Concentrator Unit (DCU) (A14)
  • Integrated Air System Controller 1 (IASC) (A55)
  • Integrated Air System Controller 2 (IASC) (A56)
  • Junction Box 2 (JB2)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Integrated Air System (IAS) Controller AMM 21-31-01-000-801
Installation of the Integrated Air System (IAS) Controller AMM 21-31-01-400-801
Removal of the Junction Box JB2 AMM 24-63-05-000-803
Installation of the Junction Box JB2 AMM 24-63-05-400-803
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 B Circuit Breaker CB2-D1. Is the fault message still present?

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

  2. Remove IASC 1 (A55). Is the message B3-006924 (ATA21) present in MDC current fault?

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

  3. Re-install IASC 1 (A55).
  4. Remove IASC 2 (A56). Is the message B3-006906 (ATA 21) present in MDC current fault?

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

  5. Re-install IASC 2 (A56).
  6. Do wiring check between DCU (A14), IASC 1 (A55) and IASC 2 (A56), through Junction Box 2, for the following wires:

    From To Result
    Conn A14EP1-10A Conn. A55P4-61
    Conn A14EP1-10B Conn. A55P4-66
    Conn A14EP1-10A Conn. A56P4-61
    Conn A14EP1-10B Conn. A56P4-66

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair wire or replace defective JB2.

  7. Replace DCU (A14).
  8. Do close out.

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