Coolant Temperature Sensor/Switch (For Computer): Description and Operation

The engine coolant temperature sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the 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.





Engine coolant temperature °C(°F) / Voltage* (V) / Resistance
(k Ohms)
-10 (14) / 4.4 / 7.0 - 11.4
20 (68) / 3.5 / 2.1 - 2.9
50 (122) / 2.2 / 0.68 - 1.00
90 (194) / 1.0 / 0.236 - 0.260

*: This data are reference values and are measured between ECM terminal (51) (Engine coolant temperature sensor) and ECM terminal (43) (ECCS ground).