Circuit Description: Notes

The DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance diagnostic monitors the sensor activity. The ECT sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The ECT sensors resistance is high when the coolant temperature is cold, and the ECT sensors resistance is low when the coolant temperature is warm. The ECT sensor is wired in series with a fixed resistor in the powertrain control module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts the voltage into a temperature reading. The PCM will receive a high voltage input when the coolant temperature is cold. The PCM will receive a low voltage input when the coolant temperature is warm. A DTC P0116 may set if the ECT sensor voltage does not indicate that the engine coolant temperature has increased sufficiently during engine operation.