Engine Temperature Sensor: Description and Operation

Engine Coolant Temperature (ECT) Sensor:

DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant stream. Low coolant temperatures produce a high resistance (100,000 ohms at -40°C / -40°F), while high temperatures cause low resistance (70 ohms at 130°C / 266°F).

OPERATION
The ECM supplies a 5 volt signal to the ECT through a resistor in the ECM and measures the voltage. The voltage will be high when the engine is cold, and low when the engine is hot. By measuring the voltage, the ECM knows the engine coolant temperature. Engine coolant temperature affects most systems the ECM controls.

A failure in the ECT circuit should set either a DTC 14. Remember, these DTCs indicate a failure in the engine coolant temperature sensor circuit, so proper use of the chart will lead to either repairing a wiring problem or replacing the sensor.