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 ECM is supplied to the ECTS via a resistor in the ECM. That is, the resistor in the ECM 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 ECM 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 output signals from ECTS every 80 sec. under detecting condition, if an output signal is below 0.1V for morethan 40 sec., ECM sets P0117. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2driving cycle.
Item | Detecting Condition | Possible Cause | |
DTC Strategy |
•
Signal low | 1. Poor connection 2. Short to ground in harness 3. ECTS 4. ECM | |
Enable Conditions | Case 1 |
•
Time after start-up > 120 sec. | |
Case 2 |
•
Time from IG "OFF" to IG "ON" > 360 min
•
Engine running state | ||
Threshold value |
•
Engine coolant temperature sensor's voltage < 0.1V | ||
Diagnosis Time |
•
Continuous (More than 40 seconds failure for every 80 second test) | ||
MIL On Condition |
•
2 Driving Cycles | ||
Temp. (℃) | Resistance (kΩ) | Temp. (℃) | Resistance (kΩ) |
-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 |
Fig.1) Normal waveform of ECTS at 90℃ (194℉)
Fig.2) Normal data of IATS & ECTS(51℉) & EOTS at ig on
Fig.3) Normal data of IATS & ECTS(195℉) & EOTS after warming up.
The output signals of IATS & ECTS change smoothly without any rapid changes. These 2 sensor have almost the same characteristic signal during the early period after start. It means that the temperatures of intake air and engine coolant are depended on the temperature of atmosphere. Meanwhile, During engine warm up the output signal of the ECT will change quicker than the IAT signal. even it may not change almost.
