If tests show that the sensor is working well and is not responsible for the observed driveability concern, scan the wiring harness and connectors between the sensor and the PCM for opens/shorts. In the case of a negative output, it is highly recommended to subject the vehicle for diagnosis by a competent repair facility. Before concluding that an ECT sensor is defective, make sure that there is adequate coolant in the system. Like the IAT sensor, the ECT sensor is also a thermistor that gets affected by the change in its temperature and is installed in the engine cooling system close to the thermostat housing to access coolant temperature. This way, the change of the coolant temperature causes a change in the resistance of the sensor and the PCM uses this information to determine engine operating temperature. A problem in the ECT sensor circuit causes a check engine light accompanied by a trouble code that originates from the wiring, connection, or the sensor. On models that include two very similar sensors placed side-by-side; one basically supplies the info that the sender in the instrument panel uses to display the coolant temperature, the other sensor supplies the same data to the Electronic Engine Control (ECT). The temperature sender has a tan or brown plastic body while ECT sensor connector usually has gray one. To exercise the ECT sensor, unplug it then use the ohmmeter to check the resistance across the terminals; at 68 degrees F, the value should be around 2,100 to 2,900 ohms. Next, crank the engine and let the engine warm up to the operating temperature point and the resistance should be in the range of 300 to 330 ohms at 176 degrees F.Since the readings are normal, look at reference voltage of PCM at the senses connector which should be about 5 volts. When replacing the sensor, use Teflon sealing tape on the threads to avoid leakage and corrosion, to remove the sensor uncover the electrical connector and unbolt the old sensor from the engine. Replace the new sensor immediately to prevent continuous leakage of the coolant; tighten the sensor nut well before reconnecting the electrical connection. After: check coolant level and add more if it is needed, start engine and wait until engine temperature indicator reaches normal level, check for coolant leaks, check coolant level in the expansion tank when the engine is cold.