DTC P0116: ECT Sensor Circuit Performance: Description

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance according to changes in engine coolant temperature. ECM supplies a 5-volt reference through a pull-up resistor(s) to sensor, which is connected to ground. When sensor is cold it has a high resistance (high signal voltage at ECM). As sensor temperature increases, its resistance decreases (low signal voltage at ECM). ECM uses signal voltage to determine engine coolant temperature. ECM calculates a modeled temperature using start up ECT, MAF, MAP and engine run time and compares this value to ECT sensor signal. DTC sets when ECT deviates more than a calibrated value from ECT modeled temperature.