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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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04/08/21

Message Overview:

Message Name:

OPN/SHRT CH1&2

Message Code:

B3-006340

Associated CAS:

None

Reporting LRU: APU EGT SENSOR
System Description: 49-00-00
Schematic Diagram: 49-61-00
Wiring Diagram: 49-61-01 Sh 1
49-61-01 Sh 2

Message Description:

Auxiliary Power Unit (APU) Electronic Control Unit (ECU) is reporting an open or short circuit for both Exhaust Gas Temperature (EGT) Sensor channels.

Possible Causes:

  • Auxiliary Power Unit (APU) Electronic Control Unit (ECU) (A39)
  • Exhaust Gas Temperature (EGT) Sensor (TC2) - (also known as Thermocouple T5)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Auxiliary Power Unit (APU) Electronic Control Unit (ECU) AMM 49-61-01-000-801
Installation of the Auxiliary Power Unit (APU) Electronic Control Unit (ECU) AMM 49-61-01-400-801
Removal of the Exhaust Gas Temperature (EGT) Sensor AMM 49-61-05-000-801
Installation of the Exhaust Gas Temperature (EGT) Sensor AMM 49-61-05-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Do wiring check between the APU ECU (A39) and the EGT Sensor (TC2) for the following wires:

    From To Result
    Conn. A39AP1-2A EGT Sensor Lug + (CR)
    Conn. A39AP1-1A EGT Sensor Lug - (AL)

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair defective wiring.
      NOTE: Lugs must be disconnected from the EGT Sensor while doing the wiring check.

  2. Replace the EGT Sensor (TC2). Is the fault message still present?

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

  3. Replace APU ECU (A39).
  4. Do close out.

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