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

Engine coolant temperature sensor (ECT Sensor)






This sensor consists of a temperature dependant resistive metal strip. The resistance of the strip varies considerably with coolant temperature, i.e, from 28 Kohms at - 30 °C to 90 ohms at 130 °C, and 300 Ohms at 85 °C. The ECT Sensor signal is vital to engine running, as the correct fuelling is dependant upon engine temperature i.e, richer mixture at low temperatures. If the sensor is disconnected or failure occurs a default value will be supplied to the system. The initial default value selected will be based on the value of the air intake temperature. This will increase to a nominal warmed up value over an individual time, programmed for each default value. The fault may not be evident to the driver, there may be a hot restart problem. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.