The electronic control module (ECM) contains
the hardware required to activate the ECI
system. Within the ECM are such controls as
the EPROM (electrically erasable
programmable read-only memory), CPU
(central processing unit), RAM (random
access memory), and also contain in the ECM
is the A/D (analog/digital) converter. The
ECM sends electrical signals to the injectors,
engine brake solenoids, the fuel shutoff valve,
and other optional items. The ECM is mounted
to a cooling plate which has diesel fuel
continually routed through it from the pump in
order to keep the internal solid-state
components at a safe operating temperature.
The engine position sensor (EPS) is required to
tell the ECM where the various pistons are and
what stroke they are on, so the correct injector
solenoid can be activated at the right time.
The oil temperature sensor (OTS) is used to
advise the ECM of the oil temperature. The
signal is used by the ECM to determine the
engine idle speed at start-up as well as reducing
the fueling rate any time the oil temperature
rises to an undesirable level.
The oil pressure sensor (OPS) is used by the
ECM to monitor engine oil pressure during
5. The coolant temperature sensor (CTS) is used to
monitor the temperature of the engine coolant.
6. The coolant level sensor (CLS) is used to tell
the ECM of a coolant level loss.
7. The ambient air pressure sensor (APS) is used
by the ECM to determine the basic operating
altitude of the vehicle.
8. The intake manifold temperature sensor
(IMTS) allows the ECM to determine air
temperature and adjust fuel rate accordingly.
9. The throttle position sensor (TPS) is basically a
potentiometer or variable resistor arrangement
that is designed to a output voltage signal to the
ECM, based on the degree of the throttle pedal
depression. The ECM is able to determine how
much fuel the operator is asking for.
10. The vehicle speed sensor (VSS) is required to
tell the ECM the road speed of the vehicle. The
VSS sensor is mounted into the transmission
output shaft housing in order to monitor the
output shaft speed.
The electronically controlled injectors receive
low-pressure fuel from a simple engine-driven
gear pump. Each injector is mechanically
operated; however, timing and duration of
injection is controlled electronically by a
signal from the ECM. This signal is referred to
as pulse-width-modulated (PWM). The longer
the PWM signal is, the longer the injector will
deliver fuel to the combustion chamber. The
greater the fuel delivery, the greater the
Two other major control switches are required with
the Celect-ECI system in order to control the cruise
control, the PTO (power takeoff), and the engine
1. A clutch switch is used to allow cruise control
or engine brake activation. It is mounted so
that when the clutch pedal is pushed down
(clutch disengaged), the clutch switch opens
the switch and deactivates the engine brake or
2. A brake switch is located in the service air line
and will remain in the closed position any time
the brakes are released. Applying the brakes
will cause the brake switch to open and break
the electrical circuit to both the cruise control
and PTO systems.
In addition to the engine-mounted components,
there are several cab-mounted controls arranged on a
small control panel that can be activated by the operator
through a series of small toggle-type switches. This
control panel contains the following:
The idle-speed adjustment switch is used to
adjust the engine idle speed between 550 and 800
rpm. Each time the switch is moved briefly to the
+ or position, the idle speed will change by
approximately 25 rpm.
The cruise control panel has two toggle
switchesone is a simple ON/OFF switch and
the other is the actual cruise control position
select switch that the operator uses to set and
adjust the cruise control speed during operation.
The engine brake panel has two toggle
switchesone switch has an ON/OFF position
to activate either a Jacobs or Cummins "C" brake
system and the other switch, used with the engine