DTC P0117-00: Engine Coolant Temperature Circuit Low Input: General Description

The Engine Coolant Temperature Sensor (ECTS) is a negative coefficient thermistor (NTC) located in the engine coolant passage on the cylinder head. The ECT sensor resistance changes with temperature change. When the coolant temperature is low, the sensor resistance is high and when the coolant temperature is high, the sensor resistance is low. The PCM supplies a 5 volt reference by way of a resistor inside the PCM, as the sensor resistance change, the voltage between the two resistors changes. The PCM uses ECT sensor values for fuel and spark control to improve engine performance.