12 © Scania Industrial & Marine Engines 2003-10:1
DEC2 CONTROL SYSTEM
This engine has an injection pump with an electromagnetic actuator which
adjusts the control rack to give the correct amount of fuel.
The system which controls the pump is called DEC2 (Digital Engine Control,
generation 2).
The control unit (DEC2) continuously receives signals from sensors for
engine speed, charge air temperature and pressure, coolant temperature, oil
pressure, throttle pedal position and control rod travel in the injection pump.
Using this input data and a control program, the correct amount of fuel for the
current operating conditions can be calculated.
The system's sensors may be used only for DEC2, not for other instruments
or other monitoring purposes.
The control unit contains monitoring functions to protect the engine in the
event of a fault which would otherwise damage it. Faults and the more
important monitoring functions are indicated on the control unit in the form
of light emitting diodes. See illustration on page 15 for a description.
In the event of a fault Power - or Shutdown on the control unit comes on as
well as the main indicator lamp on the main supply box and instrument panel.
If a fault has been indicated on the main indicator lamp, the operator can
determine the cause of the fault with the help of the LEDs on the control unit
and the troubleshooting schedule on page 18, and carry out the required
investigation and remedy.
Depending on the nature of the fault, the control system can take various
steps to protect the engine, reduce its power, allow it to run at a constant low
speed or, if a functional fault is detected, the engine will be switched off
automatically (Shutdown).
In order to read fault indications on the LEDs, there is a lamp test/fault code
switch in the main supply box installed near the control unit.
A PC based program is also available to make it easier for service personnel
to detect and rectify faults which may arise and to adjust certain parameters in
the driving program.
Only authorised personnel are allowed to carry out diagnostic procedures
and program changes.
The locations of the sensors and monitors which send signals to the control
unit will be evident from the figures on pages 13 and 14.
There is a description of the functions of the LEDs during normal operation
on page 15.
There are descriptions of LED indications when a fault has occurred and the
action taken in the case of Power- and Shutdown on page 16.
Troubleshooting and fault code reading are described on pages 17 and 18.
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