JLG 740AJ, Руководство по обслуживанию и ремонту

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SECTION 3 - CHASSIS & TURNTABLE
3121160 3-153
ENGINE MODULE SERVICE PRECAUTIONS
The Engine Module is designed to withstand normal current
draws associated with engine operation. When servicing the
Engine Module, observe the following guidelines:
• Do not overload any circuit.
• Do not probe wires for testing. This can cause a voltage
drop that would be critical to the operation of the Engine
Module.
• When testing for opens and shorts, do not ground or apply
voltage to any of the Engine Module's circuits unless
instructed to do so.
• When measuring voltages, use only a digital voltmeter
with an input impedance of at least 10 megohms.
• Do not jump start with more than 12 volts. This could cause
damage to the electronic components.
• Do not employ any non-standard practices such as charg-
ing the battery with an arc welder.
• Take proper precautions to avoid static damage to the
Engine Module. Refer to "Electrostatic Discharge Damage"
for more information.
THROTTLE POSITION (TP) SENSOR
The throttle position (TP) sensor is a potentiometer connected
to the throttle shaft on the throttle body which is built into the
electronic governor. The Engine Module monitors the voltage
on the signal line and calculates throttle position. As the throt-
tle valve angle is changed, the TP sensor signal also changes.
At a closed throttle position, the output of the TP sensor is low.
As the throttle valve opens, the output increases so that at
wide open throttle ( WOT ), the output voltage should be
above 4 volts.
The Engine Module calculates fuel delivery based on throttle
valve angle (operator demand). A broken or loose TP sensor
may cause intermittent bursts of fuel from an injector and
unstable idle because the Engine Module thinks the throttle is
moving. A hard failure in the TP sensor 5-Volt reference or sig-
nal circuits for greater than 2 consecutive seconds will set
either a DTC 12 or DTC 22. A hard failure with the TP sensor
ground circuit for more than two consecutive seconds may set
DTC 22. If either DTC 12 or DTC 22 are set, the throttle will be
forced to a 6% (idle) position.
USE OF CIRCUIT TESTING TOOLS
Do not use a test light to diagnose the engine electrical sys-
tems unless specifically instructed by the diagnostic proce-
dures. A test light can put an excessive load on an Engine
Module circuit and result in component damage. For volt-age
measurements, use only a digital voltmeter with an input
impedance of at least 10 megohms.