TM 5-3805-291-23-1
HOW TO USE ON-BOARD DIAGNOSTICS - CONTINUED
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UNDERSTANDING THE DIAGNOSTIC CODE BREAKDOWN
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N OT E
Some procedures may generate new diagnostic codes. Before any procedures are performed, make a list of
all diagnostic codes in order to determine system problems. Clear logged diagnostic codes caused by proce-
dure when each procedure is complete.
When an ECM detects an engine problem, it generates a diagnostic code. There are two types of diagnostic codes: fault
codes and event codes. Fault codes indicate a problem with an electronic control system. Event codes identify the symptom of
the operational problem and indicate how the machine is being operated.
Fault and event codes may be classified as active or logged. For active codes, the ECM records the code and a descrip-
tion. For logged codes, the ECM records the hour of first occurrence, the hour of last occurrence, and the total number of
occurrences, using the ECM's internal diagnostic clock.
A diagnostic code can be broken into four parts:
Type of Code. The screen display will show "A" for active, "E" for event, or Blank for logged.
1.
2.
Module Identifier (MID) or Event Identifier (EID).
a.
The MID identifies which ECM detected the diagnostic code. Each ECM on the machine has a unique two- or
three-digit MID. The engine ECM designation is 036, and the machine/powertrain ECM designation is 081 for the
966H. Refer to Table 1 in WP 0007 00 for a complete list of fault codes for the engine ECM. Refer to Table 2 in
WP 0007 00 for a complete list of fault codes for the machine/powertrain ECM.
b.
The EID identifies an abnormal operating condition. Refer to Table 4 in WP 0007 00 for a complete list of event
codes.
Component Identifier (CID). A CID is a number with four digits which indicates which component generated the
3.
code. For example, CID number 0017 identifies the fuel shutoff valve. Any component that can generate a diagnostic
code is assigned a CID number.
Failure Mode Identifier (FMI). An FMI is associated with either an engine or machine MID code and it indicates the
4.
type of sensor failure. The FMI is the last two digits of the diagnostic code. Refer to Table 1 in WP 0007 00 for an expla-
nation of FMI codes. FMI codes are defined by SAE standards.
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