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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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11/04/24

Message Overview:

Message Name:

SELF TEST FAULT

Message Code:

B3-681729

Associated CAS:

AT FAIL
(ADVISORY)

Reporting LRU: Autothrottle (AT) Computer
Effectivity: Post SB350-22-002
Aircraft 20937 and Subs
System Description: 22-30-00 - Auto Throttle System (ATS)
Schematic Diagram: 22-30-00-801 - Auto Throttle System (ATS)   
Wiring Diagram: 22-30-00-801 - Auto Throttle System (ATS)

Message Description:

This fault message is posted if the Self-Test fails, regardless of whether it is the brief automatically initiated test at power up, or the longer (15s) manually initiated Self-Test. Self test fault reported by the Autothrottle (AT) computer. 

Possible Causes:

  • Autothrottle Computer (A252) 
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: Review the Auto Throttle "AT Diagnostic Information", to find details about the MDC Data Reader Labels & bits.
NOTE: The MDC Fault message AT Self Test Fault is a latched Fault. The message is cleared upon starting a Self-Test, and will remain cleared if the test is successful, or otherwise re-post upon failure.
NOTE: The Self-Test will not execute in-air.  

Quick Links:

Removal of the Auto Throttle Computer AMM 22-30-01-000-801
Installation of the Auto Throttle Computer AMM 22-30-01-400-801
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
Operational Test of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-710-801
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
Operational Test of the Integrated-Avionics Processor System (IAPS) AMM 31-45-00-710-801
Safety Precautions - Maintenance Practices - ALL SPM 20-00-01-02-01
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02-01

Troubleshooting Recommendations:

  1. With aircraft Weight On Wheels (WOW), select the Autothrottle (AT) switch on the System test panel. Does the AT TEST FAULT message display?
    NOTE: The self-test shall run for 30 seconds.

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

  2. Access the MDC to view fault messages. Are there any other AT fault messages present?

    1. If YES, troubleshoot these messages first using SmartFix Plus.
    2. If NO, continue with  next step.

  3. Replace the AT computer.
  4. Do close out.

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