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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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02/10/21

Message Overview:

Message Name:

NO L-IOC-4 BUS OUTPUT

Message Code:

B3-006946

Associated CAS:

None

Reporting LRU: IOC 1
System Description: 31-45-00
Schematic Diagram: 31-45-00
Wiring Diagram: 31-45-01
23-51-27

Message Description:

L-IOC-4 data absent at L-FMC and (R-FMC -if installed).

Possible Causes:

  • Left Input/Output Concentrator Unit 1 (IOC) (A4-IOC)
  • Left Radio Interface Unit (RIU 1) (A17)
  • Left Flight Management Computer (FMC) (A4-FMC)
  • Right Flight Management Computer (FMC) (A4-FMC)
  • 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 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
Removal of the Flight Management Computer (FMC) AMM 34-61-01-000-801
Installation of the Flight Management Computer (FMC) AMM 34-61-01-400-801
Standard Practices - Wire Replace SPM 20-12-00-02
Standard Practices - Wire Repair SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset L IAPS (CB1-B6) circuit breaker.

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

  2. Swap IOCs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  3. Do a wiring check of the ARINC 429 data bus L-IOC-4 from IAPS connector A4P3 to RIU 1 connector A17P2. Repair/replace as required.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

    NOTE: An internal short of any LRUs connected to this data bus might cause this failure.

  4. Swap FMCs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  5. Replace RIU.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  6. Replace IAPS Card Cage (ICC).
  7. Do close out.

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