JLG 4394RT Service Manual - Manual (Page 145)

SECTION 3 - CHASSIS, PLATFORM & SCISSOR ARMS
3121249 – JLG Lift – 3-109
Electronic Throttle Control (ETC)
Engine speed and load control is maintained by an ETC
device. Speed and load control are determined by the
ECM. Defaults programmed into the ECM software and
throttle position sensors allow the ECM to maintain safe
operating control over the engine. The Electronic Throttle
Control device, or "throttle body assembly", is connected
to the intake manifold of the engine. The ETC device uti-
lizes an electric motor connected to the throttle shaft.
When the engine is running, electrical signals are sent
from the equipment controls to the engine ECM when the
operator depresses an equipment function switch. The
ECM then sends an electrical signal to the motor on the
electronic throttle control to increase or decrease the
angle of the throttle blade, thus increasing or decreasing
the air/fuel flow to the engine.
The electronic throttle control device also incorporates
two internal Throttle Position Sensors (TPS) which provide
output signals to the ECM as to the location of the throttle
shaft and blade. The TPS information is used by the ECM
to correct speed and load control as well as emission con-
trol.
Engine Control Module (ECM)
To obtain maximum effect from the catalyst and accurate
control of the air fuel ratio, the emission certified engine is
equipped with an onboard computer or ECM. The ECM is
a 32 bit controller which receives input data from sensors
fitted to the engine and fuel system and then outputs vari-
ous signals to control engine operation.
One specific function of the controller is to maintain
"closed loop fuel control". Closed loop fuel control is
accomplished when the exhaust gas oxygen sensor
(HEGO) mounted in the exhaust system sends a voltage
signal to the controller. The controller then calculates any
correction that may need to be made to the air fuel ratio.
The controller then outputs signals to the EPR to correct
the amount of fuel being supplied to the mixer. At the
same time, the ECM may correct the throttle blade posi-
tion to correct the speed and load of the engine.
The controller also performs diagnostic functions on the
fuel system and notifies the operator of malfunctions by
turning on a Malfunction Indicator Light (MIL) mounted in
the Ground Control Station and the Platform Control Sta-
tion. Malfunctions in the system are identified by a Diag-
nostic Code number. In addition to notifying the operator
of the malfunction in the system, the controller also stores
the information about the malfunction in its memory.
Figure 3-83. ETC throttle control device
Figure 3-84. LPG Engine Control Unit (ECM)
Figure 3-85. ECM Assembly