Engine Coolant Temperature Sensor: Notes

A malfunction in Engine Coolant Temperature (ECT) sensor circuit can set a related Diagnostic Trouble Code (DTC). For testing procedure, see appropriate SELF-DIAGNOSTICS article. An out-of-calibration ECT sensor may not set a DTC. Use the following procedure to test sensor calibration.

Disconnect ECT sensor harness connector. Using an ohmmeter, measure resistance of ECT sensor at specified temperatures. See ECT SENSOR RESISTANCE VALUES  table. Resistance should be high when engine is cold and drop as engine warms. With vehicle sitting overnight, IAT sensor and ECT sensor should have close to the same resistance reading. If resistance is not within specification, replace ECT sensor.