JLG 460SJ Service Manual - Manual (Page 209)

SECTION 3 - CHASSIS & TURNTABLE
3120895 – JLG Lift – 3-157
DTC 118- ECT/CHT High Voltage
• Engine Coolant Temperature Sensor
• Check Condition-Engine Running
• Fault Condition-CHT/ECT sensor voltage higher than
the limit defined in the diagnostic calibration
• Corrective Action(s)- Sound audible warning or illumi-
nate secondary warning lamp, disable adaptive learn
fueling correction during active fault, or any combina-
tion thereof as defined in calibration. Recommend a
power derate 1/2 to reduce the possibility of engine
damage due to the inability to sense temperature.
• Non-emissions related fault
The Engine Coolant Temperature sensor is a thermistor
(temperature sensitive resistor) located in the engine cool-
ant. Some engines use an ECT sensor that is located in
the coolant near the thermostat. Some engines use a CHT
(Cylinder Head Temperature) sensor that is located in the
coolant in the cylinder head. If the engine is equipped with
an ECT sensor then the CHT value is estimated. If
equipped with a CHT sensor then the ECT value is esti-
mated. The ECM provides a voltage divider circuit so that
when the coolant is cool, the signal reads higher voltage,
and lower when warm.
This fault will set if the signal voltage is higher than the
high voltage limit as defined in the diagnostic calibration
anytime the engine is running. The limit is generally set to
4.90 VDC. In many cases, this condition is caused by the
CHT/ECT sensor being disconnected from the engine har-
ness, an open-circuit or short-to-power of the CHT/ECT
circuit in the wire harness, or a failure of the sensor. The
ECM will use a default value for the CHT/ECT sensor in
the event of this fault.