The Engine Coolant Temperature Sensor (ECTS) is located in the engine coolant passage of the cylinder head for detecting the engine coolant temperature. The ECTS uses a thermistor whose resistance changes with the temperature. The electrical resistance of the ECTS decreases as the temperature increases, and increases as the temperature decreases. The reference 5 V in the PCM is supplied to the ECTS via a resistor in the PCM. That is, the resistor in the PCM and the thermistor in the ECTS are connected in series. When the resistance value of the thermistor in the ECTS changes according to the engine coolant temperature, the output voltage also changes. During cold engine operation the PCM increases the fuel injection duration and controls the ignition timing using the information of engine coolant temperature to avoid engine stalling and improve drivability.
Checking the engine coolant temperature under detecting condition, if the engine coolant temperature's signal is temporarily stuck above the lowest enable temperature to enable other diagnostic, PCM sets P0116.
Item
Detecting Condition
Possible Cause
DTC Strategy
Rationality check
Poor connection
ECTS
Case 1
Enable
Conditions
ECT < 50C
ECT - ECT at Start < -3C
Threshold
Value
ECT. – Model ECT < -15C
(Model temp. = f(air mass, current modeled temp.))
Case 2
Integrated air mass >0.55kg
ECT > 83C
ECT. – Model ECT >10C
Diagnostic
Time
100 sec
Case 3
Vehicle speed < 4mph for 18sec = 4 times
Vehicle speed > 30mph for 18sec = 2 times
Max ECT – Min ECT < 0.8~3.0C
Case 4
Soaking Time > 21600 sec
Coolant temp at cranking – intake temp at cranking > 26C
MIL ON Condition
2 driving cycle
Temp. (?)
Resistance (k?)
-40
48.14
40
1.15
-20
14.13 ~ 16.83
60
0.59
0
5.79
80
0.32
20
2.31 ~ 2.59
100
0.19