UNDERSTANDING THE DIAGNOSTIC CODE BREAKDOWN
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 procedure 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
description. 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:
1. Type of Code. The screen display will show "A" for active, "E" for event.
a. An active diagnostic fault code represents a problem with an electronic control system. Correct the
problem as soon as possible.
b. The Active Event Codes function provides information about events currently occurring. These codes are
similar to the active diagnostic codes, except that the event represents the symptom of an operational
problem. These codes indicate to the operator technician how the machine or equipment is being
A warning category indicator immediately follows the event code number and is in parentheses. It is a number
ranging from 1 to 3, where 3 is the most severe, and it indicates the severity of the associated code number. The
warning category provides an indication of the type of behavior and/or actions which must be taken by the
operator, or by the control system for some engine applications, to address the severity of the associated situation.
The list of codes is grouped according to the ECM from which they are retrieved. They appear in chronological
order by the most recent ECM hour of last occurrence. For a complete list of diagnostic codes and their diagnostic
procedures, refer to Troubleshooting Symptom Index (WP 0010).
2. Module Identifier (MID) or Event Identifier (EID).
a. The MID identifies which ECM detected the diagnostic code. Each ECM on the machine, except the
messenger, has a unique three-digit MID.
(1) All-Wheel Drive ECM designation is 075.
(2) Engine ECM designation is 036.
(3) Implement 1 ECM designation is 082.
(4) Implement 2 ECM designation is 147.
(5) Transmission/chassis ECM designation is 027.