Checking ECT Sensor

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

NOTE: Thermostat must be operating properly for this test to be valid. This test works best if engine was allowed to cool overnight.

Turn ignition on. Using scan tool, read engine coolant temperature. If engine was allowed to cool overnight, engine coolant temperature should be close to ambient temperature. If engine coolant temperature is more than 180°F (82°C), allow engine to cool until 150°F (66°C) is reached. Start engine. Using scan tool, monitor engine coolant temperature while engine is warming up. Engine coolant temperature should increase smoothly to at least 180°F (82°C). If temperature increases as specified, test is complete. If temperature does not increase as specified, replace ECT sensor.