The engine coolant temperature (ECT) sensor is a thermistor that is located in the lower coolant passage of the engine cylinder's head. The ECM continuously monitors the voltage drop across the resistor as it varies with the resistance of the sensor. This sensor is used for fuel/ignition control, hot/low coolant light, coolant gage, and fan. The ECM sets this DTC when the signal being received is lower than expected.

DTC P0117 will set if the ECT reads over 140°C (284°F).

P0117 is a (type B) DTC.

Caution: To avoid the danger of being burned, do not remove the cap while the engine, radiator, and surge tank are still hot. Scalding fluid and steam can be blown out under pressure.

To locate an intermittent problem use scan tool to monitor ECT temperature with Ignition On, engine Off.

Wiggling wires while monitoring ECT temperature may locate the area where short to ground may exist.

Start engine and observe ECT reading on scan tool. Under normal conditions, it should rise smoothly to 88°C (190°F).

ECT may be compared to IAT with scan tool if engine has cooled overnight. They should be within 6°C or 10°F of each other with the ignition On and engine Off.