Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
134
4.
DTC P0116 The dynamic characteristics of coolant temperature sensor are unreliable.
P0117
The coolant temperature sensor output voltage is below the lower limit (the
wiring is short to ground).
P0118
The coolant temperature sensor output voltage is above the upper limit (the
wiring is open or short to high level).
P0119 The static characteristics of coolant temperature sensor are unreliable.
Fault Description: The engine coolant temperature (ECT) sensor is a kind of negative temperature coefficient
variable resistor, which can measure the engine coolant temperature. Its resistance shall decrease with the increase of
temperature, so the signal value input into ECU in the form of voltage shall decrease accordingly. The voltage signal
range is 0-5V. The ECU searches the characteristic curve of the sensor and converts it into engine coolant temperature.
The diagnostic module of engine coolant temperature sensor shall make fault judgment based on this temperature
value. The ECU shall supply 5V voltage to the signal circuit of engine coolant temperature sensor and also supply
grounding for the low reference voltage circuit. If the signal voltage of engine coolant temperature sensor detected by
ECU is too low (indicating the temperature is too high), or too high (indicating the temperature is too low), relevant
DTC shall be generated.
The following table illustrates the difference among temperature, resistance and voltage.
Engine coolant temperature
Resistance of coolant temperature
sensor
Signal voltage of coolant temperature
sensor
Low High High
High Low Low
Diagnosis Hint:
Overheating may result in generation of this DTC. After the engine is started, the temperature of engine coolant
temperature sensor should increase steadily and become stable after the thermostat is disconnected. Test the engine
coolant temperature sensor under different temperature to check for any error of sensor. If any, the error may result in
failure of control performance. After the engine is laid up for a night, the indication difference between IAT sensor and
engine coolant temperature sensor should be within 3°C (5°F). Refer to “Temperature and Resistance”.
Check for the following conditions:
Poor contact between ECU and engine coolant temperature sensor – Check the harness connector for:
− Loose terminal
− Poor matching and connection
− Breakage of keeper
− Distortion or damage of terminal
Coolant temperature
sensor
Coolant temperature
signal (High)
Coolant temperature
signal (Low)
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