Magnum MMG25FHI, Operating Manual, Page: 32 / 60

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MMG ENGINE CONTROLLER
The engine speed (rpm) of the MMG35FHD is regulated with a Woodward Controller. The engine speed (rpm) of
the MMG25FHI and MMG45FHK units is regulated with a Governors America Corps. (GAC) controller. Refer to the
following section for information on the MMG55FHD.
JOHN DEERE ECU INFORMATION DISPLAYS AND FUNCTIONS (MMG55FHD ONLY)
The MMG55FHD has a John Deere Electronic Engine Control Unit (ECU) which regulates the engine speed (RPM)
and constantly monitors vital engine functions for a number of operation, alarm and fault conditions. When an
operation, alarm or fault condition occurs, the Liquid Crystal Display (LCD) window will alert the operator either
visually or audibly. In addition to the “Alarm List,” there is an “ECU Alarm List” which will list any faults specified by
the John Deere ECU.
Press the “  ” Scroll-Up button (on the diagnostic keypad) to view the “ECU Alarm List.” This will allow the operator
to view a description of the fault, along with the diagnostic trouble codes located at the bottom of the display. Refer
to Figure 1. To further identify a fault by using these codes, refer to the John Deere Operator’s Manual supplied with
the unit. To resume operation, the fault condition must be resolved and the code cleared from the display.
Diagnostic messages are read and displayed in the ECU Alarm List. The Suspect Parameter Number (SPN)*, Failure
Mode Identifier (FMI) and Occurrence Counter (OC) are shown together with a description (if possible). One SPN*/
FMI describes one failure. If FMI is equal to zero or one, “WRN” is displayed in the ECU Alarm list. For any other
FMI value, “Fls” is displayed. Detailed SPN*/FMI information may be found in the SAE HS-1939 Publication, or refer
to the engine manufacturer’s ECU error codes list. The following table displays the ECU messages and their
descriptions.
*Note: The Suspect Parameter Number (SPN) is displayed as “FC” on the bottom left of the LCD window. Refer to
Figure 1.
No. SPN Description
1 SPN:100 EngOil Press
2 SPN:102 Boost Press
3 SPN:105 Intake Temp
4 SPN:110 EngCool Temp
5 SPN:175 EngOil Temp
6 SPN:629 Controller #1
7 SPN:636 PositionSensor
8 SPN:637 TimingSensor
9 SPN:651 InjectorCyl#1
10 SPN:652 InjectorCyl#2
11 SPN:653 InjectorCyl#3
12 SPN:654 InjectorCyl#4
13 SPN:655 InjectorCyl#5
14 SPN:656 InjectorCyl#6
15 SPN:677 EngStartRelay
16 SPN:1485 ECU MainRelay
Figure 1