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

The ECTS (Engine Coolant Temperature Sensor) measures the temperature of engine coolant. The ECTS (Engine Coolant Temperature Sensor) is located near the thermostat housing of the cylinder head. The ECTS is a thermistor (A Variable Resistor that changes along with ECT) in series with a fixed resistor in the PCM. The PCM applies 5 volts to the ECTS. The PCM monitors the voltage across the ECTS and converts it into a temperature reading. When the engine is cold the ECTS resistance is high, and when the engine is warm the ECTS resistance is low. Therefore, when the engine is cold the PCM will receive a high voltage input, and when the engine is warm the PCM will receive a low voltage input. The signal from the ECTS is used for Injection control, ignition timing, idle speed and cooling fan control.