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.
PCM calculates the difference between the startup and current coolant temperatures and compares against the threshold. So if the difference is less than 3℃ over certain period of time PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Rationality check | ● Poor connection ● Low level of Engine Coolant ● Improperly installed ECTS ● Open or short in circuit ● ECTS ● PCM |
Enable Conditions | ● Engine Run state ● Time from IG "OFF" to IG "ON" >360min ● No Disabling Faults Present | |
Threshold Value | ● Diffence between startup and current ECT < 3 °C(5.4°F) | |
Diagnosis Time | ● Continuous (More than 120 seconds failure within 150 second test) | |
MIL On Condition | ● No MIL ON (DTC only) |
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 |
