The Engine Coolant Temperature(ECT) Sensor measures the temperature of engine coolant. The Engine Coolant Temperature (ECT) Sensor is located near the thermostat housing of the cylinder head. ECT Sensor is a thermistor (A Variable Resistor that Changes Along with ECT) in series with a fixed resistor in the Engine Control Module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine is warm the ECT sensor resistance is low. Therefore, when the engine is cold the PCM will receive a high voltage input, and when the engine is warm the PCM will receive a low voltage input. The signal from ECT sensor is used for Injection, ignition timing, idle speed and cooling fan control.
Checking output signals from ECTS every 80 sec. under detecting condition, if an output signal is above 4.9V for more than 40 sec., PCM sets P0118. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Open, Signal high | ● Poor connection ● Open or short to battery in signal harness ● Open in ground harness ● ECTS ● PCM |
Enable Conditions | Case 1 | ● Time after start-up >120 sec. |
Case 2 | ● Time from IG "OFF" to IG "ON" > 360 min. ● Intake air temperature ≥ -10°C(14°F) ● Engine running state | |
Threshold Value | ● Engine coolant temperature sensor’s voltage >4.9V | |
Diagnosis Time | ● Continuous (More than 40 sec. failure for every 80 sec. test) | |
MIL ON Condition | ● 2 Driving Cycle |
Temp. (°C/°F) | Resistance (kΩ) | Temp. (°C/°F) | Resistance (kΩ) |
-40(-40) | 48.14 | 40(104) | 1.15 |
-20(-4) | 14.13 ~ 16.83 | 60(140) | 0.59 |
0(32) | 5.79 | 80(176) | 0.32 |
20(68) | 2.31 ~ 2.59 |
