TM 1-2840-252-23-3
ITED INFORMATION WHICH CAN BE DETERMINED WITH SIMPLE VOLT-OHMMETER CHECKS.
THE INTENT IS TO ISOLATE A SUS- PECTED PROBLEM AREA RATHER THAN MAKE A FINAL
DETERMINA- TION TO REJECT THESE COMPONENTS. APPLICABLE CHECKOUT PROCEDURES
FOR THESE COMPONENTS SPECIFIED BY THE AIR- FRAME OR ENGINE MANUFACTURER
SHOULD BE APPLIED TO DE- TERMINE THE INTEGRITY OF THESE COMPONENTS.
CAUTION
ELECTRICAL PARAMETERS GIVEN IN THIS MANUAL REFLECT CHARACTERISTICS OF ACTUAL
AIRCRAFT COMPONENTS. WHEN USING THIS MANUAL IN A TEST CELL INSTALLATION, IT
SHOULD BE NOTED THAT SIGNAL INPUTS FOR AIRCRAFT COMPONENTS MAY BE PRO- VIDED
BY REPRESENTATIVE TEST CELL EQUIPMENT. IN SOME INSTANCES, THE ELECTRICAL
CHARACTERISTICS OF THE TEST CELL EQUIPMENT MAY NOT BE THE SAME AS THOSE OF THE
ACTU- AL AIRCRAFT COMPONENTS. THIS CAN RESULT IN FAULTS BEING LOGGED BY THE
DECU AND CAN POSSIBLY DAMAGE THE DECU. IF DIFFERENCES ARE FOUND, THE TEST CELL
EQUIPMENT SHOULD BE REPLACED BEFORE FADEC TESTING CONTINUES.
NOTE
Before replacing any component, be sure that a contaminated or corroded connector is not the cause of
the fault. Clean connectors with contact cleaner and blow-dry using compressed nitrogen (preferred) or
filtered dry air.
G-7 DISPLAY OF FAULT CODES
a. Code Display. All faults are classified into two main categories of criticality. Hard faults are failures which
could cause unacceptable engine and/or aircraft performance if operation were to continue in the normal
primary mode of control. Soft faults are failures which do not impact normal control of the engine or aircraft.
Fault information is logged in an electrically erasable nonvolatile memory (EEPROM), and is available through
a two-digit hexadecimal display on the DECU. See figure 201 for location of the display. The most significant
digit is used to identify the source of the faulty component, as defined below:
F -- Fluid Controller (HMU/Pump)
A -- Airframe-Supplied Sensor
D, 1, or B -- DECU
E-- Engine-Supplied Sensor
C -- Communication Between DECUs
The least significant digit is used to identify the specific fault. The codes are listed in Table 1 in numeric/ alpha
order with their descriptions and fault isolation procedure numbers.
G-4
