Engine Coolant Temperature (ECT) Sensor

The ECT sensor is a thermistor (temperature sensitive resistor) located in an engine coolant passage. The PCM/VCM supplies and monitors a 5-volt signal to ECT sensor. This monitored 5-volt signal is then modified by resistance of the ECT sensor. When coolant temperatures are low, ECT sensor resistance is high and the PCM/VCM sees a high monitored voltage signal. When coolant temperatures are high, ECT sensor resistance is low and the PCM/VCM sees a low monitored voltage. When fully warmed, ECT sensor should reflect a temperature of at least 185°F (85°C).

Coolant temperature input is used in the control of fuel delivery, ignition timing, idle speed, emission control devices and converter clutch application. A ECT sensor which is out of calibration will not set a Diagnostic Trouble Code (DTC), but can cause fuel delivery and driveability problems. An ECT sensor circuit problem should set a related DTC.