Circuit Description

DTC P0116 inspects the accuracy of the engine coolant temperature (ECT) sensor signal. The ECT sensor is a thermistor. A thermistor is a resistor whose value varies with temperature. The ECT sensor resistance is high when the coolant temperature is cold, and the ECT sensor resistance is low when the coolant temperature is warm. The engine control module (ECM) applies a 5-volt to the ECT sensor. The ECM monitors the voltage across the ECT sensor and converts the voltage into a temperature reading. The ECM will receive a high voltage input when the coolant temperature is cold. The ECM 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.