JLG 660SJ Service Manual - Manual (Page 127)

SECTION 3 - CHASSIS & TURNTABLE
3121298 – JLG Lift – 3-83
Electronic Throttle Control (ETC)
The Electronic Throttle Control device or "Throttle Body
Assembly" is connected to the intake manifold of the engine.
The electronic throttle control device utilizes an electric motor
connected to the throttle shaft.
When the engine is running, electrical signals are sent from
equipment controls to the engine ECM. The ECM then sends
an electrical signal to the motor on the electronic throttle con-
trol to increase or decrease the angle of the throttle blade thus
increasing or decreasing the air/fuel flow to the engine.
Two internal Throttle Position Sensors (TPS) provide throttle
shaft and blade position output signals to the ECM. TPS infor-
mation is used by the ECM to correct speed and load control,
as well as emission control.
Figure 3-98. ELectronic Throttle Control Device
Electric Lock Off
The Electric Lock Off device is an integrated assembly consist-
ing of a 12 volt solenoid and normally closed valve. When
energized, the solenoid opens the valve and allows propane
fuel to flow through the device. The valve opens during
engine cranking and run cycles. Lock Off supply voltage is con-
trolled by the Engine Control Module (ECM).
Figure 3-99. Electric Lock Off Assembly
Engine Control Module (ECM)
NOTE: The ECM may also be referred to as the Engine Control Unit
(ECU) in some applications.
To obtain maximum effect from the catalyst and accurate con-
trol of air fuel ratio, the emission certified engine is equipped
with an onboard computer or Engine Control Module (ECM).
The ECM is a 32 bit controller which receives input data from
sensors fitted to the engine and fuel system and then outputs
various signals to control engine operation.
Figure 3-100. ECM Assembly
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 calculates corrections for the air fuel ratio. and out-
puts signals to the DEPR to correct the amount of fuel supplied
to the mixer. At the same time the ECM may correct throttle
blade position to correct engine speed and load.
The controller also performs fuel system diagnostic functions
and notifies the operator of malfunctions by turning on a Mal-
function Indicator Light (MIL) mounted in the Ground Control
Station and Platform Control Station. System malfunctions are
identified by a Diagnostic Code number. In addition to notify-
ing the operator of the system malfunction, the controller also
stores information about the malfunction in its memory.
Figure 3-101. ECM Input-Output Diagram