Operation and maintenance manual
3-21
DDEC III & IV Operation
The DDEC system operates from a 24 volt supply. However, in the event of a
loss of power supply, the system will operate at reduced voltage. At reduced
voltage the electronic control system will detect a malfunction and the check
engine light on the dash panel will illuminate.
At this point the ECM will go into backup control and a change in engine
operation will be noticed. The engine will operate only at reduced rev/min until
the battery voltage reaches a point where it will no longer function and the engine
will shut down. The machine can still be operated when the check engine light is
illuminated, however, the fault should be diagnosed and corrected at the earliest
possible opportunity.
Note: When the stop engine light on the dash panel illuminates, the computer
has detected a major malfunction in the engine that requires immediate attention.
It is the operators responsibility to shut down the engine to avoid serious
damage.
The machine is equipped with the DDEC engine protection system, which
records the stop engine malfunction in the ECM. The stop engine and check
engine lights illuminate when the engine protection system is initiated. The
engine will immediately reduce to 70% of the available torque. Rampdown then
commences over a 30 second period and reduces the engine to 40% of the
available torque.
To allow for the possibility of the engine protection system being activated while
the machine is operating in a critical situation, a stop engine override switch is
provided. If the switch is pressed and released during rampdown, the 30 second
timer will reset, restoring torque to the level immediately following illumination of
the stop engine and check engine lights. The switch must be pressed and
released again to obtain a subsequent override.
Note: The operator must continue to reset the automatic engine protection
system by pressing and releasing the stop engine override switch at intervals
of approximately 15 to 20 seconds.