The Engine Coolant Temperature(ECT) Sensor measures the temperature of engine coolant. The Engine Coolant Temperature (ECT) Sensor is located in 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 Powertrain 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.
If ECT sensor’s resistance is lower than 50Ω or higher than 72KΩ, the PCM judged as a fault and DTC is set.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Resistance of sensor(Rcts) is monitored | ● Poor connection ● Open or short in ECT sensor circuit ● Faulty ECTS ● Faulty PCM | |
Enable Conditions | ● Time after start > 2 sec | ||
Threshold value | ● Resistance, Rcts <50Ω or ≥ 72kΩ | ||
Diagnosis Time | ● Continuous | ||
Temperature(℃/℉) | -33/-22 | -20/-4 | 0/32 | 20/68 | 40/140 | 60/140 | 80/176 | 100/212 | 110/230 |
Resistance(kΩ) | 26.74 | 15.48 | 5.79 | 2.45 | 1.148 | 0.587 | 0.322 | 0.188 | 0.147 |
Voltage(V) | 4.39 | 4.17 | 3.48 | 2.56 | 1.68 | 1.04 | 0.63 | 0.39 | 0.31 |
