Engine Coolant Temperature (ECT) Sensor

A scan tool displays the engine temperature in degrees Celsius. After the engine is started, the temperature should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens. If the engine has not been run for several hours (overnight), the ECT and IAT temperatures should be close to each other. A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. The DTC tables also contain a table to test for sensor resistance values relative to temperature.