Engine Coolant Temperature Sensor

NOTE: The following procedure assumes that the cooling system thermostat is functioning properly. Test works best if performed on a totally cold engine (cold soak).

NOTE: For circuit identification and wiring diagram, see WIRING DIAGRAMS article. After each repair procedure has been completed, reconnect all components. Perform TEST VER-2: POWERTRAIN VERIFICATION under VERIFICATION TESTS to ensure system is functioning properly.

Turn ignition on. Using scan tool, read Engine Coolant Temperature (ECT) sensor value. If engine coolant temperature is more than 180°F (82°C), allow engine coolant temperature to cool down to 150°F (66°C) before proceeding. If engine coolant temperature is 150°F (66°C) or less, start engine and monitor scan tool until engine coolant temperature reaches 180°F (82°C). If ECT sensor value increases smoothly, no problem is indicated at this time. Test is complete. If ECT sensor value does not increase smoothly, or never reaches 180°F (82°C) or more, check for cooling system problems and repair as necessary. If cooling system is okay, replace ECT sensor.