Engine Coolant Temperature (ECT)
The engine coolant temperature sensor resistance changes in response to engine coolant temperature. The sensor resistance decreases as the surrounding temperature increases. This provides a reference signal to the PCM, which indicates engine coolant temperature.
The following symptoms can be caused by a faulty Engine Coolant Temperature Sensor or circuit loose connections.
Engine Coolant Temperature Sensor Symptoms
- Extended crank time when the engine is cold
- Poor fuel economy
- Spark knock
- Lack of engine power
- Erratic and/or high idle
- Engine cooling fan stays running all the time
- Engine cooling fan fails to turn on
- Engine overheating
Engine Coolant Temperature Sensor Testing
- Disengage the engine wiring harness connector from the ECT sensor.
- Connect an ohmmeter between the ECT sensor terminals, and set the ohmmeter scale on 200,000 ohms.
- With the engine cold and the ignition switch in the OFF position, measure and note the ECT sensor resistance. Attach the engine wiring harness connector to the sensor.
- Start the engine and allow it to warm up to normal operating temperature.
- Once the engine has reached normal operating temperature, turn it OFF.
- Once again, detach the engine wiring harness connector from the ECT sensor.
- Measure and note the ECT sensor resistance, then compare the cold and hot ECT sensor resistance measurements with the accompanying chart.
- Replace the ECT sensor if the readings do not approximate those in the chart; otherwise, reattach the engine wiring harness connector to the sensor.