Monitor Description

WARNING: This page is about a different car, the 2004 Lexus IS 300. However, it is still accessible from the selected car via links, so may be relevant.

The ECT (Engine Coolant Temperature) sensor is used to monitor the engine coolant temperature. The ECT sensor has a thermistor that varies its resistance depending on the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. The variations in resistance are reflected in the voltage output from the sensor.

The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage, from the normal operating range, the ECM interprets this as a faun in the ECT sensor and sets a DTC.

Example:

When the ECM calculate that the ECT is less than -40°C (-40°F), or more than 140°C (284°F), and if either condition continues for 0.5 sec, or more, the ECM will set a DTC.