Oshkosh JLG 400S, Service And Maintenance Manual, Page: 122 / 462

SECTION 3 - CHASSIS & TURNTABLE
3-70 – JLG Lift – 3120895
ENGINE COOLANT TEMPERATURE (ECT)
SENSOR
The engine coolant temperature (ECT) sensor is a
g
thermistor (a resistor which changes value based on tem-
perature) mounted in the engine coolant stream. Low cool-
ant temperature produces a high resistance of 100,000
ohms at -40°C (-40°F). High temperature causes a low
resistance of 70 ohms at 130°C (266°F). The ECM sup-
plies a 5-volt signal to the ECT sensor through resistors in
the ECM and measures the voltage. The signal voltage will
be high when the engine is cold and low when the engine
is hot. By measuring the voltage, the ECM calculates the
engine coolant temperature. Engine coolant temperature
affects most of the systems that the ECM controls.
After engine start-up, the temperature should rise steadily
to about 85°C (185°F). it then stabilizes when the thermo-
stat opens. If the engine has not been run for several
hours (overnight), the engine coolant temperature and
intake air temperature displays should be close to each
Table 3-9. ECM Diagnostic Trouble Codes
Diagnostic
Trouble
Code
Description
11
All Systems OK
12
Throttle Position (TP) Sensor Low Voltage
14
Manifold Absolute Pressure (MAP) Low Voltage
21
Overspeed
22
Throttle Position (TP) Sensor High Voltage
24
Manifold Absolute Pressure (MAP) High Voltage
31
Fuel Pump Low Voltage
32
Heated Oxygen Sensor (HO2S) Low Voltage
33
Engine Coolant Temperature (ECT) Sensor High Voltage
35
Intake Air Temperature (IAT) Sensor High Voltage
41
Fuel Pump High Voltage
42
Heated Oxygen Sensor (HO2S) High Voltage
43
Engine Coolant Temperature (ECT) Sensor Low Voltage
45
Intake Air Temperature (IAT) Sensor Low Voltage
51
Low Oil Pressure
52
Crankshaft Position (CKP) Sensor Extra/Missing Pulses
53
Camshaft Position Sensor (CMP) Sensor Illegal Pattern
54
Engine Control Module (ECM) Fault Illegal Operation
55
Engine Control Module (ECM) Fault Illegal Interruption
56
Engine Control Module (ECM) Fault COP (Computer Operating Properly) Failure
61
System Voltage Low
62
System Voltage High