Group 23 EMS 2 Design and function
Design and function
The EMS 2-system
EMS 2 stands for ”Engine Management System” and is an electronic system with CAN communications (Control-
ler Area Network) for control of diesel engines. The system has been developed by Volvo Penta and includes fuel
control and diagnostic function. The system consists of a control module, six unit injectors, a number of sensors
that supply the control module with measurements, sockets for diagnosis and functional checks. The engine is
connected to a communications interface consisting of a CAN link and a serial link.
CAN (Controller Area Network)
The CAN J1939 link handles all communications be-
tween the engine control module EMS 2 and a com-
munications interface such as the CIU or DCU, in ad-
dition to the diagnostics that are handled by the so
called J1708/J1587 link. The CAN link is much faster
than the J1708/J1587 link. The CAN link has been
prepared to connect to other components with SAE
J1939 protocol such as instrument panels and trans-
If, for some reason, a fault develops on the CAN link,
signals for the rpm-potentiometer and the start and
stop knobs are taken over by the J1708/J1587 link.
However, instrument and indicator lamps are com-
pletely turned off. If faults develop on both links, the
GE engines maintain the same rpm while VE engines
slow to idle. The only way to shut off the engine in
this case is to use the auxiliary stop (AUX-STOP)
placed on the engine’s left side.
CIU (Control Interface Unit)
The CIU is a ”translator” between the CAN bus and
the customer’s own control panel. This unit has two
serial communication links, one fast and one slow.
The fast one is a CAN link that features a bus speed
of 250 Kbit/s. All data regarding instruments, indicator
lamps, contacts and potentiometers are controlled by
this bus. The slower J1708/J1587 link handles diag-
nostic information for, among other things, the flash-
ing code. The diagnosis tool VODIA also uses the
J1708/J1587 link to communicate with the system.
DCU (Display Control Unit)
DCU is a digital instrument panel that communicates
with the engine control module via the CAN link. DCU
has several functions, such as:
Controlling the engine
Start, stop, controlling rpm, control mode isochro-
nous/speed drop, pre-heating.
rpm, charge pressure, charge temperature, cool-
ant temperature, oil pressure, oil temperature, en-
gine hours, battery voltage, instantaneous fuel
consumption and fuel consumption (trip fuel).
Shows fault codes as text. Lists previous faults.
Setting parameters
Idling speed, pre-heating when ignition on, lamp
test, alarm limit for oil temperature/coolant tem-
perature, control mode, control gradient (VE), pri-
mary engine rpm (GE), speed drop (GE), engine
overspeed limit (GE), engine cut off, overspeed
DU (Display Unit)
DU is an instrument that displays the engine’s opera-
ting values. Measurement values are shown graphical-
ly on an LCD screen. The display communicates via
the CAN link and consists of a computerized unit for
fixed installation in a control panel.
You are connected to the CAN link between the engi-
ne control module and CIU or DCU.

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