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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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06/21/19

Message Overview:

Fault Message:

APUGCU PIN PROG/SENSE FAULT

Fault Code:

2420251LPS

Associated CAS:

None

Reporting LRU: Auxiliary Power Unit Generator Control Unit (APU GCU)
System Description: 24-22-00
Schematic Diagram: 24-22-00 [ Global Express ] [ G5000 ] [ Global XRS ]
Wiring Diagram: 24-22-01 [ Global Express ] [ G5000 ] [ Global XRS ]

Fault Description:

Auxiliary Power Unit Generator Control Unit (APU GCU) has detected a pin programming / sense fault, consequently resulting in the Auxiliary Power Unit (APU) Generator being tripped off-line or not come on-line.

Possible Causes:

  • Auxiliary Power Unit Generator Control Unit (APU GCU) (A109)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

A GCU patch cable (GSE REF # 24X-24-02) can be used to swap GCU 1, GCU 2, GCU 3, GCU 4 and the APU GCU into a different position (for troubleshooting only). You can monitor the GCU faults in CAIMS via the active faults page.

Quick Links:

Removal of the Generator Control Units (GCU) AMM 24-24-01-000-801 [ Global Express ] [ G5000 ] [ Global XRS ]
Installation of the Generator Control Units (GCU) AMM 24-24-01-400-801 [ Global Express ] [ G5000 ] [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ] [ G5000 ] [ Global XRS ]

Troubleshooting Recommendations:

  1. Disconnect APU GCU connector A109P2. Use the table below to make sure that the program pins are wired properly:
    APU GCU:

    Programming Pin From To Excepted Result Result
    Prog pin 0 A109P2-18 A109P2-34 Open
    Prog pin 1 A109P2-27 A109P2-43 Connected
    Prog pin 2 A109P2-17 A109P2-35 Open
    Parity pin A109P2-26 A109P2-44 Open

    GCU 1:

    Programming Pin From To Excepted Result Result
    Prog pin 0 A56P2-18 A56P2-34 Open
    Prog pin 1 A56P2-27 A56P2-43 Connected
    Prog pin 2 A56P2-17 A56P2-35 Connected
    Parity pin A56P2-26 A56P2-44 Connected

    GCU 2:

    Programming Pin From To Excepted Result Result
    Prog pin 0 A57P2-18 A57P2-34 Connected
    Prog pin 1 A57P2-27 A57P2-43 Open
    Prog pin 2 A57P2-17 A57P2-35 Connected
    Parity pin A57P2-26 A57P2-44 Connected

    GCU 3:

    Programming Pin From To Excepted Result Result
    Prog pin 0 A58P2-18 A58P2-34 Open
    Prog pin 1 A58P2-27 A58P2-43 Open
    Prog pin 2 A58P2-17 A58P2-35 Connected
    Parity pin A58P2-26 A58P2-44 Open

    GCU 4:

    Programming Pin From To Excepted Result Result
    Prog pin 0 A59P2-18 A59P2-34 Connected
    Prog pin 1 A59P2-27 A59P2-43 Connected
    Prog pin 2 A59P2-17 A59P2-35 Open
    Parity pin A59P2-26 A59P2-44 Connected

    1. If checks do not match the table, repair defective wiring and do close out.
    2. If all checks are good, continue with next step.

  2. Replace the APU GCU.
  3. Do close out.

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