How to test Engine coolant temperature sensor?

Engine coolant temperature sensor is also called as ECT.

The details to test CT sensor is a follows :---

TESTING

There are a few items you should check before beginning more extensive testing.

Check for poor connection at the PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections.

Look for a damaged harness or damaged wiring going to the ECT sensor, especially if heavy work has recently been done where the connector could have been damaged.

Sensor Installed in Vehicle

Fig. ECT sensor resistance value chart

1. Disconnect the engine wiring harness from the ECT sensor.
2. Connect an ohmmeter between the ECT sensor terminals.
3. With the engine cold and the ignition switch in the OFF position, measure and note the ECT sensor resistance.
4. Connect the engine wiring harness to the sensor.
5. Start the engine and allow the engine to reach normal operating temperature.
6. Once the engine has reached normal operating temperature, turn the engine OFF .
7. Once again, disconnect the engine wiring harness from the ECT sensor.
8. Measure and note the ECT sensor resistance with the engine hot.
9. Compare the cold and hot ECT sensor resistance measurements with the accompanying chart.
10. If readings do not approximate those in the chart, the sensor may be faulty.

Sensor Removed from Vehicle

1. Remove the ECT sensor from the vehicle.
2. Immerse the tip of the sensor in a container of water.

Fig. Submerge the end of the temperature sensor in cold or hot water and check resistance

3. Connect a digital ohmmeter to the two terminal of the sensor.
4. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the accompanying resistance value chart.
5. Repeat the test at two other temperature points, heating or cooling the water as necessary.
6. If the sensor does not meet specifications, it must be replaced.

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Engine Coolant Temperature (ECT) Sensor Operation?

The operating working detail for engine coolant sensor is as follows ---
Engine coolant sensor is also called a ECT.

Engine Coolant Temperature (ECT) Sensor


OPERATION


The Engine Coolant Temperature (ECT) sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°F.) while high temperature causes low resistance (70 ohms at 266°F.). The PCM supplies a voltage (about 5.0V) through a pull up resistor to the PCM's ECT signal circuit and measures the voltage. When the engine coolant is cold, the sensor (thermistor) resistance is high, therefore the PCM will measure a high signal voltage. As the engine coolant warms, the sensor resistance becomes less, and the ECT signal voltage measured at the PCM drops. With a fully warmed up engine, the ECT signal voltage should measure about 1.5-2.0 volts. By measuring the voltage, the PCM calculates the engine coolant temperature and engine coolant temperature affects most systems the PCM controls.

A technician's scan tool displays engine coolant temperature in degrees. After engine start up, the temperature should rise steadily to about 195°F (90°C), then stabilize and the thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. A hard or even an intermittent fault in the engine coolant temperature sensor circuit will set a hard Diagnostic Trouble Code (DTC).

Most ECT sensor also contain another circuit which is used to operate the engine coolant temperature gauge (if equipped) located in the instrument panel.


This details will help.
thanks.