Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Coolant temperature sensor harness is open or shorted - Coolant temperature sensor circuit poor electrical connection - Faulty coolant temperature sensor - Faulty thermostat - Low engine coolant level

When Detected

Engine coolant temperature is below the calibrated pass value

Description

The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.